In-Depth C Programming Course Summary

this comprehensive C course will take you from the basics of C programming to advanced concepts all while integrating exciting mini projects to solidify your learning this course offers a structured path through essential topics such as syntax object oriented programming data structures and more ABA teaches this course and he will help you understand C both theoretically and also gain practical experience in applying your knowledge to real world scenarios hey there free Corum ABA here join me in Walking you through everything you need to get a setup with cop let's have a quick walk through the course contents to let you know what to install for you we'll start with installing the visual studio program required to develop cop applications you'll learn about data types including integers strings and many more and how to manipulate them inside your code next we'll dive into control flow you'll discover how to use conditional statements and Loops to control the flow of your program's execution strings are essential in many applications you'll Master powerful string functions in C allowing you to manipulate and transform Text effortlessly data structures are crucial for organizing and managing data from arrays to collections you'll explore various data structures in C and learn how to use them effectively functions are the backbone of any program you'll uncover the power of functions in C including how to create and call them to organize your code no program is immune to errors you'll learn how to handle exceptions gracefully in C ensuring that your applications remain robust and reliable debugging is a crucial skill for any developer you'll discover how to use visual Studio's powerful debugging tools to identify and fix bugs in your C code efficiently finally we'll delve into objectoriented programming you'll learn the principles of object-oriented programming how to use classes objects inheritance and polymorphism to create modular and maintainable code by the end of this course you'll have a solid understanding of C programming and be well equipped to tackle a wide range of software development challenges thanks for tuning in let's get started so in order to start developing with C we need to install install the latest version of visual studio in this case it's currently 2022 so let's head over Google and type in Visual Studio 2022 download we will be presented with two links we have this one and this one we want to use a second one which says download visual studio tools so if you press on that and now we present it with the download area we have three additions Community professional Enterprise Community is free for students open source contributors and individuals which is exactly what we need for the content of this course we have the professional Enterprise Edition which paed for and only used by bigger companies or smaller teams so let's go ahead and press free download the download will start straight away after the download is complete let's start the installer so double click on the executable and press yes to allow it for admin permissions it'll pop up like this Visual Studio installer before you get started we need to set up a few things you can configure your installation you can read the privacy policy in the software terms if you'd like or you can just press continue so it's getting the visual studio installed already so so when you get to this section everything here is all the different packages and tools you can install within Visual Studio 2022 the main one that we're concerned within the content to this cause is the neck desktop environment so you can go ahead and press this one it will then tell you in the bottom right hand corner the total space required is 6.52 GB please make sure you have enough storage space available for this and then you can go ahead and press install if you want to check out other packages you can have a scroll through and read any other packages you may need and may want to install like I said the the only one required for this course is the net desktop environment you can also deal with noj development python development web development if you need to deal with individual components like specific versions you can access it here if you need some more languages installed you can access it here this should automatically select your default language for you that's based on your systems language and if you want it to you can also change the installation location in case you want to install it on a different drive or you just want it in a different folder so now that we selected the neck desktop environment ment we can go ahead and press the installation button we do have two options down here we have it install while downloading and it download all then install if you have a reasonably fast computer you can stick with the install while downloading and it will do the installation and the downloading at the same time if you have a slow computer it's preferred that you use this option to download it first and then install it just means that it won't slow down your computer too much so you can go for this one and press install now the installation will begin so now that visual studi finish installing it will say done installing Visual Studio has been successfully installed we recommend rebooting soon to clean up any remaining files so this just means restart on your computer just so it has a chance to clean up any files that were kept during the installation process so we can just press okay if you have any other versions of Visual Studio installed they'll also show up down here now that Visual Studio Community 2022 is installed we can just press launch so now it'll prompt you to sign into Visual Studio we should definitely sign in but just for now I'm going to skip but feel free to create an account or sign in if you already have one existing we can skip this and then we get to choose your theme I personally prefer the Dark theme but you can go with blue blue extra contrast or the light mode so let's select dark and hit start Visual Studio it will do a first time setup and it's already done and we're already inside Visual Studio 2022 so that's it for the visual studio installation so now that we got Visual Studio 2022 installed let's let's see how to create your first project so once you've opened Visual Studio 2022 you'll see this window popping up you can clone a repository from things like GI Hub in as you devops or open a project that you already have or open a folder which may have projects inside or you can create one from scratch if you don't want to do any of these options you can just open the visual studio program just on its own by clicking continue without code so let's go down the create a project path so click on create a new project and we'll get a list of all these different projects inside our system to be able to use the ones we going to be focusing on on this course is going to be C in the languages dropdown box and the platform is going to be windows and the project type is going to be console and they have one that uses net core which is for Linux Mac and windows and one that uses the Net Framework which is Windows so we want to go for this one so press on this one and then press next here we have our project name our location and our console app so we can start with the project name and say my first project as you can see it start copying over to the solution name as well and it tells you where the project will be created into so I'll be creating a folder called my first project which is the solution name plus my first project which is the project name inside that folder if we change the solution name you'll see update you can see here now we have multiple T's because we appended the solution name the solution name is almost like a folder that holds lots of projects inside so to begin with we'll have one solution that has one project inside and then later on in the course if you feel like you want to add more project projects to it you can just add more to this solution so let's get started and press create so now we've created our very first project and just to explain what's here we have a static main void which is the main entry point to our program if you do a lowercase M then the system is not going to recognize this main function because the down NET Framework requires this function to be found in order to run a c console app and you can see here in the errors the program does not contain a static main function and you can see it's capital M and C programming language is K sensitive so make sure to include it so now you understand how to use Visual Studio 2022 to create a project and also know where the main entry point is in C let's get started with Hello World example to kick off this course so as we know our main entry point to our application is the static void main if we go inside here and press enter then we can actually start writing some code inside here just a quick note before we continue static void main is inside the class program and the class program is inside the namespace hello world and the reason why you can tell this is because of the curly braces the curly braces of hello world begins here and ends here and Within These curly braces we have a class program and also within the class program we have the styo men so just between these curly braces we want to type console. right line open the brackets and we can type in some speech marks and we can simply Type Hello World there you go so as you can see now system has actually been highlighted so if we just delete this line you can see now system has been gr out and the reason why is it says it's unnecessary because it hasn't been used so if you undo it then this comes up because I showed you before that console right line is actually within the system Library what happens if we delete it if we delete it then it doesn't know where console exists from and because that just said system we can actually just use system. console. right line and then open the brackets and type in hello world and now this works again and the reason why this works it's because we don't have to Define that we're using system we could just use it straight in here if you have multiple lines like this then you don't want to be using syst right at the start ideally you want to have the reference to it at the top of the screen and then use it throughout so now that we've included back in the project you can see that now these have turned gray and it says that it can be simplified if we press the light bulb and we can say simplify member and it doesn't really matter because we can just delete the rest now so now that we've WR hello world let's press F5 which is a shortcut to the start button as you can see well you couldn't really see because the program closed too quickly and the reason for that is printed hello world to the console and then it didn't do anything else CU there's nothing else for it to do so the console simply closed we can use another command called console read Line open the brackets and close the brackets and have a semicolon at the end all this does is it waits here until the user inputs something reads the next line of characters from the standard input stream so although the program will actually be reading stuff we you just want this line to stop the application from closing so now if you press F5 and run the program you can see it actually says hello world and it's just waiting here flushing and this flashing means it just started this console read line so it doesn't matter what we type into here it just waits for us to press enter and as soon as we press enter this line executes and the program finishes congratulations you just wrote your first C program welcome to the amazing journey of programming so let's look at how to make variables in our C codee let's start every code with a console read line and then we can hit F5 just to make sure our console doesn't close so let's begin with an integer so integers are whole numbers so we can just say int age equals 23 so what we've actually done here is we've said we want an INT we want to call it age already made it equal to 23 this is called initializing and declaring in the same line line so what you could do alternatively is you can end the semicolon here and it just says int Edge and then on the next line you can write ede equals 23 so this is declaring it in the first line and then give it an initial value in the second line if they're right underneath each other like this case then you may as well just make it together because then you have less lines of code the reason why it says it's a green under line it's because there the unnecessary assignment because we're not actually using age so let's just print ede to the console if we make some new lines and we can type in console. right line and then press tab to finish it we can write Edge and if we run our code using F5 we can see that 23 gets print out to the screen so now that we've worked on the Edge Let's explore all data types so let's define a long variable so let's start with the type long followed by space and then the variable name that we want and let's add equals and type in a very big number so now if we hover over it it says it's a system int32 and int32 2 is actually an integer but we're telling it it's a long which makes no sense we have an in 64 here but when we hover over the number it comes up as n32 and the reason for that is when C sees that you just have a number typed in like this it will always assume that it is an integer to tell the compiler that you indeed want this to be processed as a long number then you can put a capital l right at the end now if we hover over it it says N64 and this says in 64 so so now we've got it working and we've got the long there so now we can take another console right line and just print this out to the screen and just a helpful tip if you type in CW and press tab twice then you get the console right line it's very easy to write your code and then you can type in big Follow by a tab and it'll come up straight away so as you can see they're both being printed to the console now so now that we've made positive numbers we can also make these negative by simply just putting a negative sign behind them there we go and just to show you how big these numbers are what we can do we can type in int. max value and then make another one using contr D and type an int. Min value so you can see integers can be positive 2.1 billion or negative - 2.1 billion and if we do the same for long you can see that long is a very very big number because instead of being an INT 32 it's an int64 which takes up a lot more memory so now we've covered whole numbers let's have a look at decimals so we can have a double negative for example and we can say it's minus 55.2 and in this case when you just have a number typed in like this and it's got a decimal point in it it will always register it as a double but just to make sure just as we're doing with the long you can actually just put a capital D at the end now if we print this out to the screen and also print out how big these numbers can be max value and Min value and print this out so we get our minus 55.2 and you can see that these numbers can be very big e + 308 means it's this number times by 10 to the^ of 308 which is a very big number and we also have that as a negative so we have float let's call this precision and make equal 5.1 and then put a semic call at the end now we've got a problem here this is trying to register as a double but we don't want to register double we want to register as a float and this is the same issue we have the long so when you type any number that has a decimal point in it the C compiler will always register as a double the same way when you type in a whole number it'll always register as an INT so in this case we need to put a capital f at the end and it'll process this as a Flo so now we can print this out and then let's just print out the max values and the Min values just to show you what that looks like so as you can see here we have our number printed out and again we have quite a big number 3.4 * 10 to the^ of 38 so again it's a big number and we have that positive and negative so quite a big range of numbers and the last one we're going to cover is decimal for things like money and currency 14.99 and again in this case it's trying to assign a double into a decimal so in order to denote what a decimal is you can put a capital M right at the end and for one last time let's print out the money and the decimal. max value contrl D and then we'll do Min value and you can see here that this is a really big number as well and it's even bigger than the long so we have our number printed and the Max and the minimum values so now that we've understood that how to declare a variable I have an extra little tip for you so if we had three variables int X and int Y and in in Z and let's say you're always going to declare them together like this you can actually miss out and do X comma y comma Z and that will do exactly the same thing there you go and that's really neat and it's a lot better let's say for example you had these variables but you actually had them set to something like equals 10 = 20 = 30 this is still practical but it might look a little uglier so you can actually type them in straight into here and if you comment these out again then it still works you can even put these onto new lines like this just so it looks a bit neater just prevent you from typing the additional int each time if they're all going to be the same variable type so that's it for the numbers inside our code so let's just have a quick recap so in order to Define a variable you want use the data type in this case an integer followed by the variable name and then you can either add a semicolon at that point or you can add a equals to give it a value this is just called declaring a value and this is called initializing a value if you want to decide you want to change the variable further down your program for example age equals 50 here then this is fine and this is now called an assignment it's called initialization because as soon as you make it you give it a value value and then in later on in the code if you give it another value this is called simply assigning a value this is just called assigning it a value so now that we can store numbers in C let's see how we can store characters and letters so as you know from the introduction we have a string variable so let's call that name and make it equal to Aba please note that when you're defining a string and giving it a value that this value needs to be in speech mark if you put it in quotation marks it will not accept this because that's the notation to declare a Char which we'll get on to next so on the next line we can do a Char letter equals and we can't have something like this because the Char will only accept One Singular character so we have to wrap it around the quotation mark once you've wrapped it around the quotation mark then it will accept it so let's print these two to the screen so CW tab tab and we can just print these to the screen and if we just run the code you can see that we've got the values entered in here we can start to write stuff your name is and then we can output this and we can also put it on one line if we do a console right and a console right then maybe we can take the callon off and just have it space and we can say your name is ABBA and we've seen that additional a because that's the right line for the letter so we can space it out with an empty conso right line and they'll add a gap between them both there we go so now we know how to declare a string variable and give it a value and we can declare a Char variable and also give it a value just a quick recap when you're declaring and initializing string variables you need to put the value in speech marks but when you're declaring and initializing a Char you don't have to put it in speech marks you put them in apostrophes whenever you see apostrophes that that can only ever refer to One Singular character when you see a speech mark it could be one or more characters also things can be empty this just means the string is empty this is also a valid character it just means that we're storing a string but it has no value with a Char that's not exactly the same you can't store an empty character literal it has to be given something Charles get defaulted at back sl0 which is just a default character but don't worry about that too much now we'll go into Escape characters which is the back SL later on in the course for now just knowe that whenever you declare a string variable we need to put it in the speech marks and when we're declaring a Char variable we need the quotation mark So now that we know how to define numbers in C and to also Define strings and characters then let's look at how to convert between them both so let's take some similar code from our first video and we can Define it age the number the negative the Precision and the money and we give it the same values from the first video we simply just print them out to the console here and if we just run we can see them all but this doesn't help us cuz we're just statically typing in the numbers what if these were actually processed as string and we want to convert them into an INT so just above each of the variables we're going to make another variable so we can say a string text age equals -23 and then for the age what we're going to use is this function called convert to in32 and we can put in the string inside the brackets and what this is now saying is we're taking our string text Edge which is equal to -23 and we're passing it into this function convert to in32 and the reason why in32 is because an INT is by definition an in32 which is a 32bit signed integer so what we want to do here is convert for our text age into an int32 and store it back into our int and hopefully we should see the same value when we hit run 23 so now that's actually went from a string variable and then went into our integer and we've printed out as an integer and it's no longer a string variable now we can do the same for the other ones so we can have a string text big number and make it equal to this value just in the quotation marks now we're typing this value in the quotation marks we don't need to put the L at the end the L is just to tell the compiler that we want to use N64 if we take the L away then it's going to think it wants in32 this is not re applicable when it comes to text because we're going to explicitly stay on the next line we want to convert to N64 so the compiler already knows that it's in 64 and we don't need to put an L at the end now let's make sure this works and there we go so what we should end up with is the console should look exactly the same as how we had it at the start of the video but actually what we're doing is converting it from a string into the applicable value string text negative = - 55.2 and then in here we can do convert to double add the text negative inside here and let's just run it to check and we still have the same value so it's going well okay a string text Precision make it equal to this and then instead of this we can have a convert to and in this case it's actually going to be a single and the reason why it's a single when you hover of a float the definition for a float is indeed a single so we can add that in text precision and we're just going to do the last one just check it all together text money equals 14.99 and then instead of this we can have a convert and let's have a look at this a decimal is indeed a decimal so we can say two decimal and then add the text money in perfect now if you run the line of code we can see that all of these values are exactly as we had them now they're being represented by their official descriptions Based On A String conversion as I mentioned before in the error video the problem you'll have with this is if this value actually has a character inside you will get a runtime error this can be fixed in the future when we look at how to resolve these errors and we can have exception handling and use functions like trass so we can try and avoid these exceptions occurring because when these exceptions occur the rest of our code does not run and it becomes fatal at this point but for now don't worry about this too much just get used to the notation and how these things work so this video we're going to focus on the booing data type so we can make a Boolean data type by saying Bo value equals true this Boolean value is literally just a true or false value we can store anything in here and maybe something like bull is male and we can just say it true and later on our code booleans are used to make decisions we'll cover this in the next section of this course but boings are mainly used for making decisions if one thing is equal to another thing then we can take another path or if something is true or something is false then we can do another path for example if you make an output to the user you could check if this value is true and if the value is true then you can address the user as a male and if the value is false then you can address the user as a female these are the kind of things that booleans can help us with and just like any variable if you want to assign it later on you can just assign it again and if we print these out to the screen just like that you'll just see the value is true and the values false appear on the screen as of right now in the course there's not a whole lot to do with booing just understand that they can hold a true or false value so now that we know how to define different variables and how to convert between them let's see how we can perform operations on different data types let's say we could have an INT age equals 23 and then what we can do to that age is we can say Age ++ and what this age will do is it will actually just increment age by one and if we do age minus minus it will decrement it by one so if we just print it out after and after this as well what we'll notice is there'll be no change CU it'll go forward one and then back one there we go went from 23 plus plus to 24 and then minus minus to 23 that's one of the important operators that you'll see a lot especially during the next section of this course so another way to be able to add one to a variable or anything to a variable we can replace this with age equals age + 1 and what we're seeing here we want age to have the value of itself added to one which will give us the same result is doing h++ another way of writing this is a quick shorthand is you can say age plus equals 1 these three things are doing exactly the same thing when you do an age Plus+ you can only increment by one and only one these two options give you the flexibility of having something like 10 these two are doing exactly the same age equals age + 10 and this is going to read exactly the same thing it's is when you use plus equals it will take the value of the current variable and add it to 10 which exactly what this line does to make it a lot shorter you can use age plus equals and then just put the value at the end just in case you forget to mention age twice so now if we just get rid of these two lines of code and we can just have a look and see if this runs so now the value should be 33 perfect and now as we said we're going to cover plus minus times and divide so just as you did with plus equals you can actually do a minus equals as well which will give us 13 and you can do a times equals which should give us 230 now if we try to do divide equals we're going to run into an issue it says 2 23 / 10 is 2.3 and when you take 2.3 and make it into an integer it's just going to truncate the3 and leave you with two with integers if you add two integers or take away two integers or times them you'll always end up with an integer if you divide two integers you don't know what you'll end with for example if you make this into 20 then you'll always end up with two but that's not always the case as you just saw 23 / 10 is 2.3 so if you're ever going to do any division it's best to actually make this a double cuz now that we do the division we actually get 2.3 which is technically the right value so you can add minus times and divide any variables that you want these are just demonstrated in int and double but you can do this the Flor the decimal Etc so let's have a look and see what the plus and the minus operators do when you've got a string variable so we can have a string name equals abber and then we can say the name plus equals is programming and then we can just print out name to the screen and see what happens so there you go you've actually just joined two strings together they're completely separate from each other and we've made them string together so if we try to do a minus equals you can't really remove from a string because a string is just text it'll be very difficult for the compiler and for the C language to be able to determine what's currently in the string and whether you can remove it or not this is not something that's built into the language this is not something that's built into the language so let's remove that and we can have the same thing with the TR now the problem with the Char is if we add a to B then let's see what happens to the output what it will try and do is actually get the uni code values for both of these items and try and add them together as integer variables so when you add a and b it will take the unic code value and you will actually get a capital A with a squiggle at the top and if we open character map you can see that this squiggle at the top is right here here which is unic codee 61 and 61 actually means 97 because it's 6 * by 16 + the 1 and b means it's 6 * 16 which is 96 + the 2 so you have 97 and 98 and if you add them two values together you'll get the hex code which is C3 just for this character so what you're doing is you're kind of adding them both together and you're producing weird results so unless you really want to do this then you should be worried about adding two characters together one more thing to note about when you're doing Plus+ let's bring another int variable we just say int I equal Z then we can do i++ and then if we print out I the value should be one which is fine what if we did i++ but we did Plus+ I so the value is still going to be one but what happens if we put this i+ plus straight into these brackets let's try and run it and you'll still get the value is zero that's strange because we've said I ++ and what happens when you do Plus+ at the front it will actually execute this and return the value of I and then do the Plus+ so if you actually print the value of I after you'll realize that now it becomes one after if you have had a situation where you need to increment first and then use the value you can use plus plus I now if you run it you should see the value is one twice the difference is that as the plus pluses before the VAR aable name it tells the compiler please do this action first and then return back the I if you don't want that behavior then use i++ finding the remainder between the division of two integer variables can be very handy when you're determining whether a number is even or odd let's look at an example let's have it in first Nome design the value of 10 and in second n and give it the value of three now if we just printed the screen first n divided by second n what do you think you'll get so the value of this in the calculator would be 3.3 reoccurring so we'd actually just get three because it's truncating it because of the integer so now what happens if we need the remainder between both of these you could actually work this out by seeing how many times three would be divided by 10 as close as possible and you'll see is the value is three and then 3 * 3 is 9 which will give you one left over for the 10 but that's a bit too long in our code so we have something called a modulus operator so we can actually change this divide for a percentage sign and what this will outut is it will only give us the remainder so let's say 10 / 3 is 3.3 as we've just said but the remainder is different remainder is exactly how you learned it at school 10 / 3 is actually three remainder 1 because 3 * 3 is 9 and then you have one left over to get to 10 so that'll be 3 * 3 which is equal to 9 and then one left over to get to 10 so now let's run our code and see if we do actually get one there we go so the best way to determine if a value is actually odd or even is to divide it by two so we can say 10 modulus 2 and if the value is zero then that means the value for first num is actually even if the value is one one then it's odd let's see how this works out if we had 10 modulus 2 then the value is zero because 10 can be divisible by two perfectly let's say we had 11 modulus 2 the closest multiple to 11 is 10 which is five and then we have one left over so you just have the remainder is equal to one and if we just keep going up in the chain we'll realize that it's the same pattern every single time you go up a value the value just toggles so when we print this out to the console and the value is actually zero that means the number is even and if we make the number odd on purpose and then rerun the code you can see that it's a number one now which means this value is now odd so let's look at a couple of examples and see if you can figure out the answer if we do a th000 modulus 90 what do you think the value will be and let's write a couple more if we do 100 modulus 90 and maybe something like like 71 modulus 10 so have a think about this in your head and see if you can figure out the answers pause the video and see if you were correct let's take a look at the answers so we can see we have 10 10 and 1 so the closest multiple to 1,000 from 90 is 990 so we have 10 left over to get to 1,000 and the same goes here the closest multiple of 100 to 90 is just indeed 90 so we only have 10 to get from 90 to 100 and in this case the closest multiple of 71 to 10 is 70 and we have one to get up to 71 therefore these two answers are indeed correct so now that we know how to really Define a variable by specifying that type followed by the name and given it a value let's see how we can do a very easy way of defining a variable so normally we would type in Edge but we can use this VAR keyword and what this means is the compiler will figure out what type it needs to be based on the value we initialize it with so if we just make a variable called age then it's not going to like it because you need to give it a value this doesn't give the compiler enough information to figure out what this variable is going to be just because it says age this is just text to the compiler this does not mean anything so if you make it equal to 23 then the compiler can see that this is indeed int 32 because it knows that so now if you hover over VAR it says in32 now let's try and do this for the big number our big number equals 90,000 and what will happen now is because it's defined as in32 it's going to say this is in32 as well and this is the same issue we had we'll move first def finding the long variable in the first video we need to explicitly give it an L just so this knows that it's N64 and now the VAR has updated to an in 64 instead of rewriting each one we can just change each to V and inspect what happens double double and now we have a float single single and finally the decimal we have a decimal and we have a decimal and the same thing goes for a string we can say V name equals ABA and we can have a v letter equals a there we go and they'll both register as there pickable data types as a string and as a CH and if we just print this out to the screen to make sure everything's working fine and run the code you can see that everything is exactly how we'd expect so just a quick recap you don't have to do this at the end of the day this will be exactly the same as writing this because when our code gets compiled down it doesn't matter what these things are cuz the compiler will deal with it however way it wants to this is just for us to read it in some cases if the value is very obvious like as we know an age cannot really be a point 23.1 years old no one says that in real life when you get asked your age so we can just assume that this value is going to be an integer and that's fine because that's an easy number that's an easy example but if we say we want a negative or a big number then it doesn't really tell us what we're meant to be like this big number could be somewhere up to 2.1 billion which is what an integer supports but in this case if it's going to be a big number and we specified the L then we're going to need a really big number bigger than 2.1 billion so in my honest opinion it would be very beneficial to only use VAR if it's very obvious what the variable is going to be and what it's been assigned to using VAR too much might hurt the readability of your code in the future because you have to inspect each variable individually to read what the type is going to be if you're scrolling through your code and you can see that this is along very quickly and you don't have to hover over it then it can improve your read time this is really important as readability of code will make more sense when it comes to Big projects when you have 20 30 lines just like this project then it makes almost no difference cuz it only takes a couple of seconds when you have big functions and big software when you work at a job then it's going to be very difficult to be able to find your way around and to understand what's going on especially if you're new to the code something very simple like this where you know you're defining a name it's very obvious and V will be accepted fine because you can tell that this is always going to be a string there's no other data type in C gets specified by a speech mark whereas when you're defining numbers it can be very very hard to understand what different data types that people are using throughout the code especially when these numbers are not statically typed in they might be inputs from the console from the user from a different function from anywhere so having good variable names along with their explicit types will be very handy to understand code in the future so now that you've understood how to make a variable let's look at a concept called constants so we defined a variable called vat and we set it to 20 just to represent the 20% vat in the UK now later on in the program we can actually change it to anything we want and that's because it's a variable variables can change in certain circumstances like vat you might not want to change it and you want to disable the ability to change it to out the code if it's done accidentally let's say for example you're making a banking application and you want to fix the vat and you don't want anyone else to change it you can add this keyword called const right before the Declaration and now when you go to reassign it you'll get an error message and it says at the left hand side of the assignment so anything before the equal sign has to be a variable property or indexer and in this case if you hover over vat it states that it's a local constant local because there's no access modifier before it and constant because we specified the cons keyword so now if we try and run the code we'll actually get a compile error because the vat cannot be changed so if we remove that and then we just print out to the console using CW tab tab and then we can put V8 in the brackets and press F5 and now we can see our 20 being printed so let's try and calculate some values using this code if you have an in Balance make it equal to 1,000 and let's say we wanted to calculate the vat based off this then you'd have to do a little bit of a complicated calculation you have to take the balance and because the V is a percentage we need to convert it from decimal to percentage so if we do times and then open the parentheses we can insert vat divided by 800 and just to make sure that this gets processed as double we want to write 100 D cuz right now it's in 32 and if we leave this as an integer division then we'll lose any decimal places and decimal places are very important when it comes to percentages so we put a 100 D at the end now you can see it says double so it'll actually calculate as if it was a decimal number so now if we print that to the screen so we can see here that 20% of the balance is indeed 200 instead of having to do this calculation each time what we can actually do is make another const this I'm making it a double cuz we're not sure what the output of this division will be and we don't want to truncate it so we want it as a double and we can say percent vat and what we can do here when we assign the value just because it's a constant it means that we can't change the value but that also means we can read it as many times as we want so we can say the percentage V is actually the current V that we've got specified here ided 100d this will give us the vat from a number form into a decimal form so now when we do this calculation if we duplicate this line using contrl D we can remove these entire brackets and literally replace it with percentage vat and you should see we get the same values perfect this can be very helpful in the future if you have things like version numbers in your code you can have version 1.0 and then if you ever specify this version later on in your code you can just change it once up here and it will change the rest this can be very helpful you'll avoid a lot of typ and you won't have to redeclare this value several times if you had three different occasions where you displaying the version number in your code then it's going to be problematic once you update the version number and you have to change every single occurrence and you might miss them so inserting it once and only having to change it once is the preferred option just to note with constants when you compile your code all the constants will actually do is do a find and replace so it will take this vat and find all references of vat and just drop the 20 in there so this is more of a feature for maintaining your code from a user and programmer's perspective rather than anything to do with the compiler because when it compiles it just removes all the constant anywhere and then you're left over with the literal values that we've gave it nonetheless this is still something very handy to learn and to use throughout your code first you want to Define a variable to hold your name so we can just say string name equals abber perfect so that's the first one achieved says Define a VAR able to hold your phone number so at first this could be quite easy we could say int number equals and then we can start to type our number in here so now that's our number completed let's move on to holding your age and we can just have an INT age equals 23 print variables line by line to the screen so we can use CW tab tab and type in name and then we can use contrl D to copy and paste the line then we can do number crl D again and then we can use Edge now if we run the code let's see what happens here we've actually hit a slight problem it says 1 2 3 4 for the number but I'm pretty sure that I started off with zero this is a problem with storing your number as an integer as a number zeros at the front don't really matter if we had 100 zeros here then it's not going to change the actual value the only time zeros matter is if it's throughout the number or towards the end that actually changes the number but if we have lots of zeros at the start then it doesn't change anything so what you actually want to do in order to store a number is you want to store it as a string therefore when you run the code it will actually return the zero that we typed in so now that we've accomplished all of these let's see how we can Define the variables using the VAR keyword so if we hover over these you can see that it's picking up that it's a string and a string here and finally this is an integer so what we can do very simply is just change these to VAR and then let's hover over the variables and just see if the tool tip reads the the correct data type string string and integer and if you run the code you should see no difference so in this exercise I want you to create and initialize two integer variables make a variable to work out the remainder output the remainder to the screen and then change the first integer variable to another number recalculate the remainder and output the new remainer to the screen so let's take this step by step so first we need to create an ize two ins let's say int num 1 equals to 10 int num 2 equals to two make a variable to work out the remainder so we can have an INT remainder equals to and if you remember how to do the remainder it uses the modulus symbol which is the percentage sign so we can say num one percentage num two now it says output remainder to the screen so we can use CW tabtab add remainder in and hit run and just for now we can see that the remainder is indeed zero if the remainder is zero then that means 10 is even because 10 modulous 2 gives us zero and if it's zero then that means it's even if the remainder was one then it would mean it's odd so if we try 11 remainder two we get one so 11 is indeed an odd number so let's change this back to 10 and then it says change the first inter variable to another number so just after here we could say num one equal 11 and then recalculate the remainder so we essentially just need to do this section again and we don't need to write into before these two variables cuz int is only used when you're declaring it this is reassigning the variable so we reassign variable num one to 11 and then we reassign the remainder to the calculation again and now we can use the exact same line of code above to print out the remainder to the screen now you can see that it's 0o and one it's zero because 10 is even and it's one because 11 is odd so far throughout the course we've been using console right line to Output stuff to the screen for example I can output hello my name is Aba and we can see it in the console the issue is so far we haven't really wrot any code to be able to read in values from the console so let's explore that option right now so in the console Library we have a console right line but what you don't realize is we can also use this console right line to ask the user a question and to let the user type something in so let's use CW tab tab and say enter your name with a colon and then end the quotation marks and then in order to return a value from the console into your program we need to use console. readline and if you hover over readline let's have a read at description reads the next line of characters from the standard input stream perfect this is exactly what we want to do right now it's to use at the end of our code just to stop the console from closing so we can actually see the output so if we just run this right now we actually get the opportunity to type but when we press enter our program closes this is because in this case we're simply using readline just to wait until the user has pressed enter so so our program doesn't close but what you don't actually see is this is returning as a string which means that anything that we type into here and when we press enter it actually gets a return back to the code but we not doing anything with it because we don't care at this point so now let's actually do something that will make us care about the user's input so we can make a new string variable and assign it to console readline and it should give us the ability to store Whatever Gets entered inside the console so we can just do string name and we can end the semicolon here and if you wanted to on the next line you could do name equals console. readline or if you wanted to have it all in one line then you can get rid of the semicolon and bring it up like this this is the preferred method as both lines were on top of each other and it wasn't really necessary to split them here we're doing a declaration of string name and an initialization and giving it the value of console. readline and this is whatever value the user is going to type in let's run our code and see what happens enter your name abber now when I press enter it's successfully stored abber inside this string name variable and now it's waiting at this line the console read line just right here so when I press enter the program closes so now that we've made a variable and not done anything with it let's print out to the screen to make sure that something's actually worked so if we use CW tab tab and we type in name in the brackets and we can run this code again and let's see what happens as soon as I type in Abba and press enter then this second abber is actually the variable printing out to the screen so here it says enter your name with a colon and normally when you see the colon it sometimes lets you type on the same line so if youd prefer the user to type on the same line then we actually have another function for that instead of using right line we can just use right and the difference between right line and right is the right line will actually have a Terminator at the end of the line to tell the console that he wants to push everything after it onto the next line whereas console. right will just print it out to the screen and not worry about any new lines let's try run it now and now we can type in and as you can see it's a little close to the colon so we can fix that in a second so you press enter you can see now that abber comes up on the second line so if we just put a space after the callon just to give it a bit of room now if we type in abber you can see that there's a bit of a gap and it's quite nicer to look at now if we press enter you can see that Abra has been stored successfully so what we can do now is maybe ask for your age so we can have a console. right enter your age age call on space and then do a string age equals console. readline and then we can have a age output as well and let's see how that works so we can say abber then say 23 and press enter and now we have abber stored within the name variable and have 23 stored within the age variable so let's try and output a string that's a bit more meaningful to the user let's clean this console up and see what we can do so we don't need to Output their result back to the console because they literally just type that in and we don't want to have this line because we just use that as an example so if we run the code right now it'll look better but it does look a lot more structured enter your name and then enter your age so now when you press enter the program will just close so let's try and output these two variables in a formatted fashion so as you now know we can use console. write to print a lot of stuff on one line so we can use console. write and we can say your name is and then add a space and finish that line there and then duplicate it down we can write name duplicate that down and say space and your age is duplicate that one down and then we can type in age and let's see what happens now abber 23 there we go so we actually have the name output and the age output all on one line if we all change these to right lines then they're going to be on separate lines and it's not going to look very nice so I'm just going to introduce you to a notation called string concatenation this is the notion of being able to concatenate two different strings which just means to add one string onto another as you can see this is taken up four lines of chorde and it's getting a bit ugly the better and easier way to do this is by containing it all within one line so we can have a console right line and we can take the first section your name is keep the space at the end we can end the speech marks and put a plus and then we can say name so now we've just added these two together if we just comment out the rest of them and run the code and you can see that they should be on one line there you go so we can say your name is ABBA and let's just keep changing the plus symbol so we can say and your age is another space and the speech marks and plus the age now we've got all of this contained within one line and it looks a lot better enter your name abber and into your age 23 and now you can see exactly the same output but reduced to one line as you can see these three lines are all stuck to each other so if you wanted to add a blank line between these two you can just put an MC console right line just in here and what this will do is simply just print the right line character to the screen which will force the console to make it on the next line just like so here's the console right line from the empty line that we just wrote and this is the console right line to Output the values so now that you've understood how to read values in from the console let's try and convert some values as I showed you how to do it earlier on in the course you can actually convert these strings into integers ideally you want to store variables in their data types as we covered before ages should not be stored as strings they should be stored as integers but if you try and change this to an INT then you're going to have an issue console read line will return back a string so therefore it can't implicitly convert from a string to an integer so we need to do this in two steps we can rename this to age input and then on the line underneath it we can say int age equals convert to int 32 and then add age input in these brackets there we go and now when we actually print the line of code nothing should actually change your name is abber and your age is 23 but now what's actually changed is we're storing the the variables in the correct format this is the ideal method because in the next section when we cover if statements you'll realize why this is very important if you wanted to minimize the amount of steps you need to convert this then you can actually move the console read line and get rid of the string input variable and we can just paste it straight into the bracket of the converter in 32 and you can get rid of the string input variable and everything will work the same AB 23 and now it's working exactly the same if this is many steps for you or if this looks too complicated then just please revert it back just to keep it the same way for the time being so now we've learned how to read in values from the console and output them back to the screen now let's see how we can use if statements to divert our code into multiple paths so in the previous section I told you that it is very crucial for our code to have this int Edge and the reason why is age is meant to be stored as a number and not as a string so we read it in first as a string and and then convert it to an integer using this function and store it into our age variable this is the reason why so our condition goes as follows we write the word if and between the brackets this needs to be evaluated to either a true or false value and then we can have the curly braces to tell us what to do if this becomes true so in this case you want to just check if our age input is greater than or equal to 18 let's say this was an entrance to a place that only allowed overes to enter so we can do a input which references the age input variable and we can use the operators equals greater than greater than or equal to less than or less than or equal to or not equal to so these are all the different options that we have we can say if the age input is equal to 18 perfect so now that we've read in the age input we can check if it's 18 let's just process a message in here says you are 18 and let's have a look and see if this works AB 18 now I press enter it says you are 18 but this is the problem with storing everything as a string and then trying to use it as if it was a number if I type in 18 followed by a space as you can see there's a blank Spacey now and press enter you can see that it doesn't come up and the reason why is it's processing it like this with a space at the end in order to avoid situations like this this is why we would convert it to a number and the reason why we're using equals to here is we can't use greater than or equal to because strings can't be greater than or equal to another string they can only ever be equal to or not equal to string is just text so if something equals to something then it's fine the only way that we can use these different operators is if we actually interact with our integer variable now let's see how we can use this so we can say age equals equals 18 and now you can see we actually reference it as a number now let's run the code if I do 18 Follow by space it still works and the reason why is it actually dismisses that space when it's converting to the integer so now age is stored as an integer and we can actually manipulate this a bit better so instead of saying you are 18 we can say you are 18 or Alo and now instead of doing equal to we can have greater than if we have greater than then we're actually dismissing the number 18 because if the age is greater than 18 so this will read like this and 18 is not greater than 18 so this will return back false what we actually want to use is greater than or equal to if the age that we've inputed is greater than or equal to 18 then you are 18 hence the equal to or greater than if you're older so now let's try and run this abber 23 perfect you are 18 or older let's change so let's change some other if statements to add some additional conditions so we can say else if and the only reason why it would come into this bracket if this condition returns false it will move down the next condition in the else chain if this was wrote as a separate if statement then this would run completely independently from this one if you're going to have chained if statements you need to make sure that you chain them correctly in this case I want to check if it ages between 18 and 25 and then move on to a different age bracket and these two things are grouped together so we should have this as an else if because with an age bracket you can only be part of one age bracket and not multiple so we can say if age is greater than or equal to 25 and we can copy this and we can say you are 25 or older now let's see what happens enter your name abber and let's just say that I am 35 it says you're 18 or older but I told it the program I was 35 now the problem we're facing is any value that's over 18 will always enter inside here and it will skip over this one completely this is not the behavior it that we want so what we can do in our if statements is we can use the double pipe which represents or or the double Ampersand which represents and and we can change some conditions in here to make sure that you implement some sort of range so we can actually have a range between 18 and 25 so we can say if the age is greater than or equal to 18 and the age is less than or equal to 25 and we can tweak this message you are between 18 and 25 and let's just run that for now and see what happens ABA 25 now it says 18 and 25 so now that we've got between 18 and 25 here we can tweak this to be greater than or equal to 26 if you're 25 will'll enter this condition and if you're 26 or older into this condition so let's test that now if we enter 35 now it says you're 26 or older that's perfect because now that we've implemented range checking it gives us the ability differentiate between different age groups more precisely let's Show an example of how to use the all so if we just have a block comment around all of this we can write an if statement in here and we can say if the edge is smaller than zero or the edge is bigger than 150 then we can output to the screen inv valid Edge and what this is saying is if we're less than zero and notice that this is less than zero so this value will actually start at minus one and this value start at 150 is minus one or less or over 150 then this will happen notice why it's an r one of these need to be true in order for this to be true when you've got an and both sides need to be true in order for this condition to evaluate is true so let's try our code we can say and we put minus one one and now it says invalid age which is perfect because this is our range checking and we can try again with 151 as it's just outside the range it will say invalid age and if we have an else on here we can print valid Edge notice there is no condition in here if you have an open else like this it means If This Were to return false it will always do this regardless of any condition in this case is it's perfectly reasonable to do this because we know that any values that are underneath zero or over 150 is invalid and anything between 0 and 150 is indeed valid what you can do instead is actually move these if statements inside here so instead of just printing out valid age we can actually check the age as well so let's run this now and we can say Aba minus one and it will only print out invalid age and then move on because once it reads this line of codee it will actually skip over the lse and finish up down here and now if you enter a real value you are between 18 and 25 so let's follow the path it got to here and realize that the range track was actually correct so it jumped out of this curly brace and went to the else because this had returned false we jump into this else and now we start checking if age is between 18 and 25 which it was because our age variable is 23 then it outputed this to the screen now if we do the same thing but have 35 instead then it follows the exact same path except towards here this will return back false and then it will check the next condition if age is over 26 then we'll return this so now let's just make a quick multiplication program using if statement to see if you can get the answer correct so let's just comment everything out and we'll start the next section underneath so let's make a console. write and ask the user to enter the first number and then we can say int number a equals convert to int32 and the value that we want to convert is a console. readline which is whatever the users entered from the console again if you're unfamiliar with this format you can just type it in manually number a input equals console readline and then we can put the number input in here now if you use shift and highlight these lines and press contrl D we can duplicate this entire section and we can say enter the second number change a to B change a to B and then finally change a to B perfect so now we've got into the first number and enter the second number and we can say our answer equal to number a multip by number B and then we can have a console. right value of you can add to it number A plus an X Plus number B and then finally plus a callon for the user to type in and then we can say string answer input equals console. readline and then int actual answer equals convert to in 32 and then we can have the input in here so now that we've got one number from the console the second number from the console we're just making a variable that will multiply them together and store inside answer and then we're just going to ask the user what's the value of number a times my number B and they can input that we store it as a string and then convert it to an integer and store the answer into actual answer so now just after the section we can write an if statement that says if the answer equals to the actual answer then we can say Well done and else and the reason why we don't need a condition this else because with equals to the only opposite thing you can have is if it's not equal to so if you really wanted to you could also right if answer is not equal to actual answer then in here you can say close but it was wrong you don't actually need this this is just for learning purposes because this will return back false if they're not equal to each other so this statement is just a given if they're not equal to each other then we can just assume that they're not equal to each other so so we don't need this additional statement if this condition evaluates to being false then that means they're not equal to each other we don't need this additional check to check if they're not equal to each other because that's a given if this returns back false so we can just leave this as an else let's try run the code 10 10 value of 10 * 10 100 now it says well done and let's just try that again and we can enter a different value 90 Clause but it was wrong so let's just have a quick recap so in the previous section we talked about how to input from the console and we generated this line of code which will output your name and your age in one line to the console and then we looked at how we can use these different operators in our if statements and we did some range checking to check if the age was between 18 and 25 and it would output something to the screen and if it was over 26 you'd get a different output to the screen and then we took that a little bit further and started using the r operator if the age is smaller than zero or it's greater than 150 then it must be invalid and if this condition returns false it must be between 0 and 150 so we can come into this L's bracket and inside here we can do our range checkin from the previous bit of code we can check the ranges between 180 and 25 and print a value or if it's over 26 we can print another value and you can keep changing these if you want you can have 26 to 40 and 40 to 60 etc etc that's up to you so this is just a quick little program to simulate multiplication program we can enter the first number using console. right and then we start it as a string and we put that string into the convert in 32 function to give us back an integer variable and we do exactly the same thing for the second number and then we make a variable to store both numbers multiplied by each other we ask the user what is the value of number a Times by number B and we give them an opportunity to type in a value we read that value in convert it to an integer store it as an into actual answer and then in our if statement we say if the answer is equal to the actual answer then we print well done to the screen double equals are used for equality and single equals are used for assignment don't get them mixed up we don't need an else condition in here because if this returns true then this will execute if this is indeed false that they're not equal to each other then we always want to do this section and we don't need to put an additional if statement inside here if you wanted to but it's not necessary you can have else if answer is not equal to actual answer but this is just extra code and it hurts the readability and it should be avoided if statements are one of the methods we can decide different paths in our code the next method we can use is called switch statements so let's write a little program so we can demonstrate this so we can just have a console. right enter a date of the week and we can have in date equals convert to in32 and we can place our console. readline inside the brackets so we take whatever the user typed into the console and then place it inside here and inside here we're going to convert whatever they've typed in to an integer 32 and star it into our D variable so if we just print this out to the screen to make sure it's working fine if we just type in seven we can see that seven is returned so it's all working so normally what we do is type if D equals equals 1 and then we can add the curly braces and use CW tab tab and we can print out Monday now if you run the code and try use number one then Monday works and that's fine and then let's do another lse if and we can say day equals equals 2 and then we can print Tuesday perfect so if we try that now there we go so now we have the ability to print out Monday and choose it to the console depending what day the week the user enters but since we're going to have seven different paths because we got seven days of the week then sometimes it might be better and cleaner to use a switch statement so let's have a look at the syntax so we can type in switch and then inside the brackets it's what variable we want to have a switch on so in this case we want to be using the day variable so we can add day in the brackets this is not a condition in the brackets this is just telling us what variable we're going to be using for the switch statement so let's open the curly braces after and inside here instead of having paths like this we're going to use cases so this can be translated to in the case of number one we can do this in the case of number two we can do this so let's try and see how it works we can type in case followed by number one and then add a call on and then we can type out our Monday in here and then we need to follow each case off by finishing the section off with a break this break is very essential and you'll get a syntax error if you don't put it in so now if we do case two and we do exactly the same thing there we go and if I dismiss the break then you'll realize that it says it cannot fall out so we have to use a break just the compiler knows that we want to break here the reason why this break is placed inside here is because what we can do is we can say case two and then add another one in here called case three and what this now reads is if we enter two it says Tuesday and if we enter three It also says choose it so what you can do is you can actually chain so this would be equivalent to writing if D equals 2 or D equal equals 3 now this is exact translation these two are exactly the same as of right now we have D equals equals 1 which is our case 1 and then equals 2 or equals 3 is right here if we go into the case 2 path it will fall in the case 3 so we're saying for this break is we want to end this section here so now if we just revert this back and continue the chain I'll just skip this part just so it's a little bit quick there we go so now that we've got all seven days of the week let's just see if it works let's try six and we have sat it so now we're kind of missing something from here the only thing we're missing is having our external else just in case the user types something invalid so normally we would write something like this enter value between 1 and 7 just to make sure that the user knows what they're doing now we don't seem to have anything inside here that gives us the opportunity to it in invalid so we have this keyword called default and it works exactly the same as the case except what this will do is this is basically the word that replaces else so we can literally take this line of code and place it again over here and add ourselves a break this is exactly the same as doing our L statement inside here if none of these cases match this variable then it'll go into the default and continue as normal so if we type in zero we should see the message twice because it's executing for the if statement and executing down here and let's do eight and you see the message again so now that the case statement is fully working let's just comment out the if statement and make sure that it's still works one Monday let's just try another one and we can do seven for Sunday so just a quick recap case statements are used by using the keyword switch followed by the variable in question and then if you want to check if this variable number is equal to something you put that something straight after the word case followed by a colon and then you can insert multiple lines of code inside here and make sure you end that line with a break if you want to chair in multiple like Dayal 2 or Dayal 3 then you can add the case above right here so the case of zero or the case of two it will do this little section so it'll print out choose there if the user enters zero or the user enters two of course in this case we don't actually want that after you filled out all of the code make sure you add something called the default the default is equivalent to an lse keyword in our if statement just to catch all the Val use in case the users type something incorrect and you want to let them know what they should be typing instead so now that we explored different paths in our code using IF statements and switch statements let's have a look at how we can iterate through our code an iteration in code is just the ability to be able to Loop and do a certain task so let's say we wanted to print high to the console several times then we just have to copy and paste it down and this will be five separate lines that do exactly the same thing this will essentially achieve what we want the problem is you just have exactly the same code copy and pasted so what we can do if we just block comment this line for the time being we can write something called a for Loop a for Loop gives us the ability to Loop a certain amount of times depending on the parameters that we give it so this is the syntax you can type for open the bracket and we have to use a variable so we can declare a new variable straight into these brackets we can say in I equals z and then have a semicolon and there's three different sections of this the first one is the variable decoration and initialization and the second one is the condition so in this case we want to do this task five times so you want to say I is less than five then we end that semicolon there and now for the third task every time this fall Loop goes around we want to increase I by one because we want to go in steps of one so we can do i++ alternative if you don't like using Plus+ you can say I = I + 1 or to make that quicker you can could say i+ equals 1 I personally just prefer using Plus+ and you'll see that everywhere else there is certain cases where you would actually you want to change this to a different value like i+ equal 2 and we'll show you that in a second so this for Loop now says we want to go from ials Z and once this condition returns back false when I is equal to 5 or greater then we want to stop this for Loop every time this forp goes around so when it hits this curly brace and comes back around we want to do this action and in this this case it's I ++ so if we just use console right line and print out the value I we can see what happens when the follow runs you can see that the value of I is increasing one each time and after the fifth time is increased the value is actually five so now this statement is false because the value of I is equal to five so therefore this is now false and the fall Loop is ended so now that we've verified that you can repeat it five times using this code we no longer want to print I we want to print our high so let's paste that inside the bracket and run the code now you can see that these two values will be exactly the same as printing it out to the console just like this but now we have a lot less code so let's have a look at another example we can say 4 in I equal 0 and we can say I is less than or equal to 10 and then we can do i+ equal 2 and then if we just print I to the console so what this is now saying is I want to go from zero all the way till 10 and I want to go up two times each time so what this will be achieving is printing out all of the even numbers between 0 and 10 let's try and run it now we can see we have all the even numbers printed out between 0 and 10 because we're going up in twos if we start this at one for example and still keep every parameter exactly the same then we'll be getting all of the even numbers between 1 and 10 11 is missing because our condition stops at less than or equal to 10 what you can also do with for Loops is you can let the user determine what this value is going to be let's test that so if we block comment this section out what we can do is we can append this little section so we can have a console. right how many times do you want to say hi can have a callon followed by speech marks and then we can say int Loop counter equals convert to n32 and we can have console read line inside the brackets how many times you want to say hi the user types in the value we take the console read line as a string convert it to an integer and St inside loop counter so now what needs to change inside here the five is what determines how many times that we're going to Loop so in this case we actually want to just Loop by whatever the user types in the counter let's just type five and make sure it works and if we just type one it works if we type zero however however it will just skip over the for Loop and the reason for that is if you're going from zero to I is less than zero then this is immediately going to be false so then the for Loop is just going to get skipped immediately there is nothing to do if the user is typed in zero which is perfectly reasonable and you can type in a really big number like a 100 and it will output them all to the screen if the user types in zero then nothing's going to come up so you always want to be able to let the user know if there's something wrong so we can say if the loop counter equals equals to zero or maybe we can change this to less than or equal to cuz it could type in minus numbers as well we could just say conso right line using CW tab tab sorry please enter a value above zero and then if this condition has returned back false then inside our else statement we don't need to give it an else if because if it's less than or equal to zero then we want to process the other values because it has to be greater or equal to one so when this is false this section has to be greater than or equal to one so we can just place our for Loop inside here and that's fine and let's try to run the code now and if we type in zero please enter a value of zero and if we just try any negative values we'll get the same message if you want to print additional code in here you can literally do anything you want you can even ask the user what they want to print up here and then you can replace this with a message for example we can have a string message and we can just change this to hello world and this could be something that you read in from the console so we can say message and we can put that in here and if we print that there we go so we can just say console. right what do you want to repeat and then we can read this in and actually it might be easier if we change this Loop counter to Second so if we highlight the section and hold alt and press down arrow twice we can move it down and say and how many times do you want to repeat it there we go so now what we can do is we can use this message inside here and then Loop depending on how many times the users typed in whatever so we can type in hello world get this exact value and we can say 10 times there we go so now this entire program is fully customized by the user's input so let's just have a quick recap so we started off this code by printing the console right line five times to the screen we wrote Our simple far Loop that went from in equal Zer to I is less than 5 and we did I ++ because we want to count up in ones you can place the high inside here and it'll printed it five times for us so now we've made our code from five lines down to just three lines for the for Loop and then we allowed the user to type in how many times that they want to repeat it and we change the condition from I is less than five to I is less than whatever the user has typed in installed within the loop counter and then we hit a problem where if we entered zero anything less than zero the F would just not run and it might look like some things went wrong so we added a little if statement in here to make sure that the user has entered a value above zero and if they haven't we can let them know we don't need another if statement in here because if this has returned back false we can assume that the value is something that we can work with we later tailored the program so we can change this message that was fixed to high to something that the user can type in manually so now that we know how to use for Loops let's have a look at while Loops for loops and while Loops still iterate through code but they're used in slightly different contexts for Loops are used mainly when you know how many times you can iterate through as in this example we're going to printer the console exactly 10 times but in a y Loop you might print until a condition is true for example if you asking the user to type a number and they kept typing in something else you don't know how many times it's going to take the user to type in correctly so in that case you would use a y Loop if you executing a certain amount of code and you're only doing it a fixed amount of times then it's always best to use a for Loop so first let's try and convert this simple for Loop that just prints I to the console 10 times just like so from zero all the way till 9 so let's comment out this for Loop and have a look at this Syntax for the while loop so we can type the world while and then in here we have our condition and then we can open our curly braces and while this condition returns back true it will always go inside the curly braces and when this condition returns back false then we'll exit the while loop so let's try and mimic exactly what we're doing inside here there's three sections of the for Loop we Define the variable that we're going to use for the for Loop counter and we give it an initial value we give it the stop dring condition and we give it how many times the value needs to go up every time the fall Loop iterates in the while loop situation we only have the condition available so let's take our condition and paste it straight into here and now we need to store our variable so just because it's a while loop when we can't store it inside here we have to do it outside the Y Loop so let's make it in I and we'll make it equal to zero so we've got our variable we've got our condition now we need to set I ++ so inside the Y Loop we can say i++ and then now we've achieved this entire line and successfully converted it let's try and put the console right line in and see what happens and let's run the code so it's going from 1 all the way till 10 and the reason why it's gone from 1 till 10 not from 0 to 10 is because the i++ is at the start let's move it down online using alt and down arrow key to move it down and let's run it again and you can see it goes from 0 to 99 and if we just block comment this out and undo the for Loop you can see that they're doing exactly the same thing so let's bring the W loop back and as you can see what we have is we've defined our I variable made it equals to zero while the I variable is less than the value of 10 we print the I to the console and increment I by one and we keep looping this until this statement returns back false and then exit the Y Loop and jump underneath the curly braces and hit the console read line and this is the output that we've got so now I've just copied the code from the if statement video and let's make this code a little bit better so let's comment out our while loop and our for Loop that was just used for explanation purposes and this is the code that you saw earlier on in the C we read in the first number start as a string use that string to convert to an integer star number a and Then star number B and these two blocks are exactly the same except you have have enter first number and enter second number and we store number a and store number B then we store the value of them both multiplied inside our int answer variable then we ask the user what's the value of both answers times together give them a chance to input their value convert it to an integer and then we check the value and print well done of close but it was wrong now if we run this code again and we type in 10 and 10 and we know the values of 100 but let's just type in 90 now this is kind of a problematic user case we've asked the user to type in a value and they've got it wrong and then when they press enter the program just closes there's no opportunity to Loop or try this again so what we can do is add a y Loop in here and we can say while the answer is incorrect we can keep asking the user to keep on guessing so instead of reading the input here let's turn this little section into a question what's the value of number a * number B and instead of allowing an input here let's just put a question mark and then let's add a console right line just to give a little bit of a gap and then in order to do our while loop we actually want to create a bolean variable just to track if the answer has been correct or not this is the section that we want to loop around in the while loop we want to read in the user's answer check it output a message and then give them the opportunity to read in another value so they can guess again while the answer is not not equal to the actual answer then we can loop around our code so we have to modify a few things here so we can't just take this code and place it inside the problem with doing this is the variables that we want to check answer is outside of this y Loop but actual answer is inside and the reason why there's a red line here says it does not exist in the current context because we're trying to check a variable that hasn't been defined yet so what we can do is take the decoration for the actual answer and place it outside here and make make it equal to zero and instead of redeclaring it inside the while loop we can take this in and get rid of it so we set the actual answers to zero set the answer to the multiplication while the answer is not equal to the actual answer then we want to loop around so we don't actually need another check in here this while loop will keep on repeating if the answer is incorrect so we don't need a path for correct and incorrect if this while loop still continues then the answer will always be incorrect so what we can do to double check is we can say if the answer does not equal the actual answer then we can place this message inside here and get rid of this branch and then after the while loop has continued we can say Well done so let's just read through the code while the answer is not equal to the actual answer and when this while loop first enters it's going to be true because you're going to have 10 * 10 which is 100 and the value of answer is zero so this will return back true cuz these two values are not equal to each other then we're going to ask the user to enter the value then we're going to read into the actual answer check if they're not equal to each other and then we output a message because we're asking a question here we want to ask another one using a console right Line enter your answer call on here we go so let's have a look and see how this works 100 100 what's the value of 100 * 100 and let's just get it wrong on purpose 90 call is wrong and now we get to answer again and we can keep answering this as many times as we want until we reach the correct answer which in this case is 10,000 and we've got the answer well done so to make the console look a little bit better cuz this is all in one block we can separate these with console right lines maybe after this line we can print out a new line and then after each guess we can print out another new line so after each guess we'll be down here we can just print out a blank console right line and just after after you ask them to enter the second number we can print another one here and let's just see how that looks 10 10 now it looks a lot better because you ask the user to input the numbers then you ask them the question and then you get the answer and then it keeps looping around like this so there's a little gap between each one so you can efficiently read it instead of it all being closed off together and now if you answer it correctly 100 now it says well done and when we press enter again the program now closes so that was using a while loop and now we have something else called a do while and a do while is very close to a while except that the while will only happen if this condition returns back true and a do while will always happen once and it'll check the condition at the end so let's have a look and see how this works so we write the word do and then we have the curly braces and then after it we have our while condition and let's just copy the condition from the old while loop and we can say answer is not equal to actual answer so as you can see with a while loop it will always check the condition first and then it opens the curly braces in the do there is no condition it will always do everything inside the curly braces once and then it will check this while condition if this condition is still true then it'll loop around and check it every time but it will only check it at the end while Loops will check the condition as the first thing it does and then check it every iteration so let's move our Corde down into here and let's just comment out our while loop just to see how this works and if we run it again to make sure it's working fine 10 10 90 90 50 and then finally 100 and it says well done so you could be thinking what are the differences between a while loop and a do while in certain cases you want the while loop to make sure this condition is true before even continuing in this specific case we always want the user to answer the question it doesn't matter if it executes once because actually that's the behavior that we want we've asked the user a question right here so we want to always be looping at least one time the while loop user case doesn't quite apply here because we don't necessarily have to check if they've answered correctly if they haven't even inputed a value yet we always want to be able to give them the option to do it once and then we check their answer at the end they could get it on the first answer 10 10 100 and it'll still be fine the same is true with a while loop but it'll B easier and it makes more sense to read your code when you have a while loop you can see that this bit of code depends on a condition whereas in a due while the first iteration does not depend on anything but the second and third and so forth depend on the condition so depending on your user case and what situation you want to use it you should either pick a while loop which will only occur through a condition or pick a do while that will occur once or multiple times after the first condition has passed so when you have if statements that are pretty basic you can actually make them quite easy to read through the conditional operator also known as the Turner operator so let's see how this works let's say we have an INT ede and we set it to a minus value and we know that this value can never be someone's age because it's negative but let's say that we have a situation where you ask the use it for their age and they've accidentally typed in -10 and we know that that value is not actually true so we could write something like this age is greater than or equal to zero then we can print out valid and then in the lse we can take this console right line and we can print out invalid so that means if we run our code now you can see that it says invalid and if we change it to positive 10 now it says valid so this seems a little bit long we are just checking one condition printing a value and printing another value if that condition returns back false so our conditional operator works like this we have a condition followed by question mark then the value if it returns true then the value if it returns false let's see how you can rewrite this if statement into one simple line so let's take this in steps these two values are both strings that we've typed in so let's make a string and we can call it result and let's make it equal to our Turner operator so the first step is to get the condition and the condition in this case if the age is greater than equal to zero we can follow that by a question mark and then if this returns back true we want the string to say valid and we can have a call on and if it returns back false then we want the string to say invalid and we can add a semicolon and then straight after it we can just have a console right line that just says result as you can see now that we get it twice we can verify one comes from the if statement and one comes from from the turny operator and now if we make this a positive 10 then you can see it both says valid so if we comment out the if statement and just see this running on its own just to double check there we go and because this is just returning back a string we can actually just take all of this code in the conditional operator and paste it straight into the console right line so you run the line of code now we get exactly the same thing if this hurts the readability of your code then it's best to just store it and then use it after if you can read this code and it's better for you in the long run later on you might want to dismiss this variable and do it straight inside the brackets just to save a variable and then print it out to the screen straight away it'll be better for memory if you just print it out straight away but if you're not familiar with this notation yet and you want to get used to it then that's fine as well so a quick recap we had an if statement with a condition and if this returned back true we printed valid and if it return back false we print invalid and this is pretty simple the only difference between these two paths is this string literal that we've typed into here so we can pull the string values out and place them in our conditional operator we can say string result is equal to if the age is greater than or equal to zero then we store valid inside result and if it's not greater than equal to zero then we can start inv valid straighten our string after we've start this value we can print results straight to the screen which will either give us valid or invalid when you're dividing two numbers you might get an ugly output just like this the user sometimes doesn't want to see such long decimal places and maybe you just want to prevent it to 81.3 in order to do this we need to use a format pattern so the language understands what we're trying to achieve so if we make another console right line what we can do is use string. format and inside the brackets we can give it a format and then the object that we want to format so in this case the object in the second parameter is our value so let's open some speech marks go to the next parameter using the comma and just type in our value and then inside the speech marks we want to type in the pattern if you type in curly brace as zero then zero represents the first value in this list we can do a space followed by curly braces one and then add another comma and we can add a thousand and what this means is value will get placed where zero is and 1,000 will get Place one is so let's run this and you see the exact same thing's happened plus a SP and now we have the Thousand which follows this part exactly if this is confusing don't worry too much about it I have the next section all about string functions so let's get rid of the one followed by the thousand and run it again and we should see the output being exactly the same there we go so now let's see how we can make this better in terms of decimal places so just after the zero and the zero represents the first value value we can add a callon and this callon will tell us what format we want the value to be displayed as we can type in 0. and what this means is all the numbers before the decimal place will get displayed and only two numbers after the decimal place will get displayed so let's try run this now and you can see that the code output is a lot cleaner one thing to note though by default this will round it up 0.37 becomes 0.4 not to worry though cuz this is what the user will see on the screen and it won't affect the actual value of the variable if we print out value straight after you'll see that the difference hasn't been changed it's still 0.3 in the original variable so that's one method of doing it what we can do now is just use contr D and copy it down and we can use different formats to show you what it looks like if we remove the 0 and then one of the zeros and leave it like this and it grains one decimal place each time you'll see what the output looks like we just have the 81 which essentially makes it into an integer because it's a whole number then we have 81.0 and the reason why it's 0 Z is cuz 0.3 will round down as it's under 0.5 the 03 is going to round down as it's under 05 so it'll round down to zero and then finally we have the 81.4 and just like before this will round down to4 and just like before this will round down to 0.4 this will round down to 04 let's say you wanted to get rid of trailing zeros because you don't want them then you can actually change this zero to a hashtag once you onun the hashtag then it will trim off any trailing zeros so what this means is it will try and put it in this format but if this format happens to be a zero then it will just keep it like this and if you just have 81 dot then it'll also get rid of the dot for you so then you just left with 81 it's really up to you as the programmer what you want want to display depending on what context I'm just giving you the options that you have available so let's say we want to work with money now and we have a 10d divided by 3D and what that value would be is somewhere between 3333 and this will be reoccurring cuz it's exactly 1/3 the reason why I've got D's in here is because these are registering as doubles if you type the value in normally it'll get registers an in32 and the problem with in32 is when you do this division it will process the division is an integer and then store it as a double the issue with that is in this case and in this case both values will get truned let me demonstrate if I remove the D from both sides and down in here it will see what the difference is and let's print out money and then's see what's happened in the first case this isn't actually an issue because we have a decimal place here which means this will be a double so an integer divided by double will give us a double but we just place the D here just so we don't forget and and it makes the compiler's job a lot easier cuz it doesn't have to convert it from an integer to a double and in this case we have an INT that's divided by an INT so we'll get 3.3 reoccurring but because it's processing as an integer then we just get three being displayed and this is not the intended result so let's just replace these back to D's and we'll see what we get now which is a 3.3 perfect so let's say that we want to display this as actual currency because you never see it displayed like this it's always to two decimal places just as follows so we can follow the same approach as above we can do string. format 0 call on 0.00 and the curly brace and then common money cuz that's the variable in reference and now if we run that let's see what happens 3.33 that's perfect and now what we can do in here because this is the pattern we can actually type in anything before after this and it won't affect the pattern just like so we've added some Extra Spaces in here so if we get rid of these spaces we can actually just place a pound sign in front of it and then let's see what happens when we run it perfect so now we actually have some money and we can say in here £10 /3 equals this and now our output looks a little bit better because we have some formatting now the issue is when we start getting into negatives let's see what happens so we can say -10 /3 equals something and when we run we'll see that the format is actually incorrect now you never see the negative symbol after the pound symbol it's always this way around in this case what we're doing is we're telling the compiler hey we only want to see two decimal places but always keep in this format the pound sign followed by the value and the value of money is -3 so it'll Place -3 inside here and then add the pound sign before it but we don't don't exactly want that so we can add something called a culture info but we can also give it some other formatting some other way so let's explore some other options if you use money to string then what we're actually doing here is using the double variable and converting it to a string and we get passed back a string representative of this value and that's fine and when we run the code you'll see no difference between these two at this point they're both being converted to Strings but what we can do in this case is when we open these brackets it tells us there one of four what does this mean exactly so in our two string function we have four ways that we can call this function the first way you give nothing in the brackets and if we press the down arrow the second way is to give it a format provider the Third Way is just a string format and the fourth way is both a format and a provider so we'll use all of these in a second but let's explore the easiest one if you add a string in there which gives us the third overload string format and we can just type in a Capital C let's just see what happens perfect so now we have the best format displayed to us and the reason why this works is the C program will recognize that the format of C is telling us that we want to display currency so then it's going to your local machine and figuring out where you are based on your date and time just down here when you have adjust date and time it will figure it out based on this we have UTC time and we have the date and time listed up here based on that information it can figure out that we are indeed in the UK and we want to display a pound sign and because the program knows that it's - 3.33 it'll put the pound sign in the right location so now that we've explored C let's have a look at the other ones that are available so if we use contrl D and copy this down three times we can use C 0 C1 and C2 and now if you run this again you'll see what the output gets you c will get your currency in its most native form which is what we're used to using in the UK C zero will only return you back with the whole number C1 will give you one decimal place and C2 mimics C on its own as they're displaying the same values now this is where it gets interesting if you want to display a different currencies then you're going to have to use this thing called a culture info which will be able to retrieve back different currency formats based on a certain country code that you give the function so let's have a look and see how that works if we scroll to the top we can add a new library called system. globalization inside globalization we have a culture info so let's see how we can tailor these to make it look a lot better if you're worried about different currencies so we use CW tab tab and we do the same thing money. two string we add our C and this is where our format provider fits in so we can start typing culture info it should come up like this press enter and inside this is a class that's why it went green if we press dot then we get the current culture the current culture will decide based on the machine that the program is running on if this program is running on a cloud computer and the cloud computer is stored in Europe then it might display euros and if it's stored in America then it'll display dollars so you want to avoid using current culture if you're going to scale your program worldwide in the case of this example I'm going to leave it because as you you can see when I run it it will display the same thing as the other ones because this one will also recognize that my current culture is UK and I'm also telling it to use the current culture so in both of these cases it's figured out that my current culture is indeed the UK and it started using the pound sign but let's say we want to give it a different culture then what we can do if we duplicate this line using contr D and remove this section just after the dot we can actually say create specific culture and inside the parentheses we can actually add a string and it says here a predefined culture name or the name of an existing culture info object the name is not case sensitive so in the case of the UK you have English GB and now we need another bracket at the end and then if we use controll D to copy this down we can change GB to us let's run this again and see what happens these two don't actually output anything different because we're just doing the normal culture and then we're telling it to find the GB culture which is exactly the same thing for me so we get these two values exactly the same and apparently it's picking up that in the US you have brackets around your negative values which I can't personally validate but this is how it's showing up so let's try some other cultures and see what happens so we can try Au for Australian then you can see that they actually use a negative followed by the pound sign and then the value so even though they're both in dollars one's US Dollars and one Australian dollars and apparently the US uses brackets for the negative values but Australians use the negative value like we do so let's just have a quick recap so we can display the value just like this but we'll have a problem with multiple decimal places we can use these former options to give us zero decimal places one or two decimal places and then when we use this format the problem with it was when you display negative numbers you get a nasty form format where the negative value actually comes after the pound sign which is not correct and you don't want to Output that to your users instead you should use the C format to tell the compiler that you want to process this as a currency currency processing is better because the software will understand that the value you're trying to represent depends on a certain strict format just as follows you don't want the negative to be here instead of before it because that doesn't look very nice to the end user alternatively you could use this CI info if you're going to scale your program scaling your program means that it's going to live on servers and this culture in for especially the current culture depends on where the program is being run on because it depends on the system time different servers will have different dat times set because they'll be in different countries so you want to be careful and if you want to display in a certain currency you can create a culture specification and pass the country code inside the brackets and then you'll get the correct output and it doesn't matter where your program lives if you always want to generate in pound symbols then you always use create specific culture and always specify NGB upon doing so you'll always get the pound sign and it doesn't matter where your program lives so throughout this course you've seen this notation a lot print out value using console right to give the user an opportunity to write on the same line reading their value as a string and store it in a variable and then use that variable able to convert it to an integer 32 and we're passing the string input inside here and then we convert it to an integer if we run the code you can see that this actually works perfectly assuming you actually enter a real number like 10 we press enter and it works and it outputs back to the screen using this console right line and if you press this restart button we can start the program again and let's say we accidentally type a character like L and we press enter and we've get a format exception now this is problematic because our program will now close if we press continue it doesn't even hit this line or this as soon as it hits the exception in here our program just closes if we use debug start with our debugging and now we're actually running the program outside of visual studio so we won't get that pop up when the error happens let's see what happens if we type this in now we can say 10p and press enter and now we get that the program stopped working you've probably seen this pop up a lot throughout Windows and different versions of Windows because when a program has a fair little error or an exception you see this popup appear and the only thing you can do is either debug or close it normally the debug option isn't available but because this is a c program and it's made through Visual Studio and the visual studio is being installed on the system then it gives us the option but really all we can do here is just terminate the program it doesn't matter what happened because we can't recover this if we press close then it's literally just going to close down it's going to tell us the exception and then press any key to continue and it's as you press any key then the program just closes so this is very fatal for our code since if we had some precious data stored in here or anywhere else in the program it is now lost before we can do anything this is problematic and we want to avoid this the best way to do this is to use something called trass right here the program is assuming that your string input is a perfect input and then you're immediately converting it to an integer now like I said what if this had 10 H in it the program is going to cause an exception and then the program is going to close so let's see what we can do with this trip pass function so the notation is int. trass the first parameter is a string s string s is a string containing a number to convert so what this tripassure equivalent a return value indicates whether the conversion succeeded okay perfect so we'll get into that in a second so our string s is a string containing our number to convert and in this case we want to be using the num input so we copy and paste that down and then we add a comma because we have more than one parameter now we have an out int result when this method returns result which is our integer contains the 32bit sign integer equivalent of the number contained in S and S in this case is our first parameter which is num input if the conversion succeeded then we get the value inside our result or zero if the conversion failed the conversion fails if the parameter s is null or string empty is not of the correct format or it represents a number that's less or more than the maximum value that the integer can stall this paramet is p uninitialized any value originally supplies in result will be overwritten let's dive in to see what this means because it's an out in result what this means is we can actually process a variable inside here like in Num so we can say out num and what this will do is when this line executes it will try and convert num input and place the value inside num so we don't need to run this convert anymore we can just specify that num is equal to zero so we've read in the string that contains our 10 H and we have our num that contains zero let's just remove this console right line so now we have our variable set up let's see what happens if we do a conso right line and just print num after this let's see what happens to the code so if we type in 10 H and press enter the value of num is zero but what you notice now the program hasn't caused because it's tried to pass it instead of just passing it automatically and then cause an exception so the reason why Try pass is called try pass is first it tries and then if it succeeds this will contain the value and if it doesn't succeed this will contain zero to know if the number has actually been converted we actually have to use the bull return value so what this means is because it returns us back a bull we can store it inside a bull and we can give it the name of success bull success equals into. trass we try and pass the num input and we place the value inside num the reason why having this bu success is very very essential let's say for example the user actually enters zero so technically as of this point num zero is actually correct because we've got zero and we initialize it to zero but of course after the trass runs this is still going to be zero now we don't know if the value zero is because this has succeeded or the value is zero because we initialized it to zero let me demonstrate if I type in a zero here is this zero being converted because this was successful or is it presenting me zero because this has been initialized to zero and the only way we can know is because our trip pass will return us back with true if s was converted successfully otherwise false we can actually write an if statement in here if success open the curly braces and we can start to type something in here so we can take our console right line and place it up here using alt and up Arrow key and then in the L's we can say failed to convert so now we have a mini setup here if it's been successful we print out the number if it hasn't been successful then it'll go into this path and it'll print fail to convert let's have a look and see how this works now if I press zero and I see Zero that means it's followed down the success path and this zero actually means it's converted my input instead of just the value that it's being initialized by if you run the code again and type in 10 hit then we actually see it says fail to convert and why that happened is we have 10 H appear and then this will return back false when it tries to convert num input and then after it hits this line since success will be false it will Dodge this path going into this path and output fail to convert what you can do if you really wanted to is you could wrap this around in a while loop so let's see what we can do so we can specify a bu's success and make that equal to true and then we can add a while loop with success in there and then open the curly braces and put all of this code inside here now we're going to have some errors because we got success twice but what we can do which will be a lot easier is we can place this straight inside our bracket and the reason why is because this returns us back at Boolean so we don't need to store it and then use it another thing we can do is instead of having Inn and then num right here you can actually make this a declaration as well so if we just remove this value we can write out Inn and this will do exactly the same thing it just uses less variables while our success is true we come into here and run this code if we fail to convert then we still want it to be true so we can loop around if we've converted it and the value is successful then we can actually make our success at this point false cuz that will stop the W loop from going around let's run the code we can type typ in 10 H 10 a 10 a etc etc and as soon as we type in a real number then it'll print out and the while loop will cancel and now right here we're set on the console readline now if we press enter the program will close so let's have a recap we use in. TR pass so we can try and pass a value before the program assumes that the value is in the correct format we give it a string variable and it returns us back with a fresh new integer called called num or whatever you want to call it inside here we can place this straight inside the condition of an if statement because this function returns us back with a true or false value otherwise known as a bull if this has been successful we stop the while loop and print the value out to the screen and if it hasn't been successful then we print fail to convert and because our success is still true it will L back around to the start of the while loop and ask the user to input another value to try and convert this Loop will only exit if it's indeed being successful and the only way it can exit is by having the success being equal to false and the only way that can happen is by having a successful conversion the use of trip pass in every program is very essential because if you have a fatal exception then your program will close and you will lose all the data the problem with that is you might lose anything that you haven't processed yet at that given point in your program so you want to try and use trass because you'll avoid any potential exceptions and you can let the user know if the conversion has been successful or not and write yourself the same while loop just like this so you can tell the user hey you input it incorrectly but this is how to do it right and make sure that your program doesn't execute incorrectly and make sure your program doesn't just close unexpectedly and then an error will be caused in this exercise I want you to print out some sort of times table and what I mean by this is you want to ask the user us to input a number for the table and then write a for Loop to print out the x * table X is dependent on the value that entered if they enter 10 in here then this will be the 10 times table let's get started so we can have our normal console. write enter a number and then use our int number equals to convert to in32 and we can say console. readline because we want to read whatever the user types in then we have a four into I equal 0 I is less than 10 we're only going to print up to the 10 times table so 1 * Something 2 * something all the way up to 10 times the value that they entered immediately we acknowledge an error here when you do your 10times table for example you do 1 * 10 2 * 10 and so on and so forth the issue here is we're going from 0 to 10 but because it's less than 10 we're actually going from 0 to 9 so let changes to one and then less than or equal to 10 in both cases we were actually looping the same amount of times the issue is this was starting on one and the other one was starting on zero and the first one was finishing on nine and this one's finishing on 10 and we want them to go from 1 till 10 instead of from 0 till 9 even though that's the same amount of iterations it gives us different values so in here we can just have a console right line and this is how it's going to work work we're going to have our first number times by our second number and that's going to be equal to something so our first number is our value of I cuz that will say 1 time something 2 * something and so forth our second number is whatever the user has typed into the calculation which will be number and our third number is going to be the actual result of the calculation which are these two times together so we can have I star number and that should be it let's run it and give it a shot we can do our 10 times table and if we press enter you can see that it's fully working this will be our I variable going down the side the second number is what the user typed in and the third number is this multiplied by this gives you the output let's run it again with a bigger number and it seems to handle okay and because this is an integer you'll expect to work okay up until around 2.1 billion which is a big number for some times tables anyway so just a quick recap we Loop through from 1 till 10 instead of from 0 to 9 because we made sure that when we do our multiplications we don't want to start the value at 0 * something we want to start the first one at 1 time something and we don't want to end at N9 we want to end at 10 so using one and less than or equal to 10 will get us the values that go from 1 till 10 and that will make our output look a lot more concise we're using conditional format in here adding the zero and curly braces and then the one and then the two and in order to insert the values in it's a comma delimited list after the speech marks the first one goes in the right order zero is I one is number two is I times the number running that code we will get this output there you go so in this exercise I want you to have a look and see if you can make the Fizz bu game Fizz bu game is one of the most popular interview questions you'll come across and the way to do this is to create a for loop from one to something in this case I'm just going to use 15 and inside the followup you want to decide if the number is divisible by three and five then you want to print FS buuz if it's divisible by three then it's Fizz five it's buzz and if it doesn't fall into any of them categories then you want to simply just print the number out to the screen let's get started so we can have a four and because we know how many we want to do we want to do in I less than 15 I ++ and then inside here we need to use the modulus operator which is the percentage sign so if you remember from the tutorial in order to figure out if a number is odd or even you could do the number modul is two and if that value is one then it must mean it's odd and if that value is zero it must mean it's even but what we can also differentiate from here is if 10 modulus 2 equals 0 then that means that 10 is divisible by two but also it is even and if it's even that means it's divisible by two if it's not divisible by two that means it's not even and therefore it's odd so in this case if we try to divide three and five we can have the same calculation but we can work it out differently so 10 modulus 3 actually gives us a value of one because it's three remainder one so if this value is anything other than zero then we know that these two were not div divisible by each other 9 percentage 3 equals 0 which means it's divisible by it so in our if statement we can say if I which is the number that we're currently up to percentage 3 equals equals to zero and because we want to check for five as well we want to say and I percentage 5 equals equals to zero and that means they're both divisible by each other so we can do a console right line and we can say fiz buzz and then in else if we're going to check if it's three and we can repurpose this exact condition because this just checks if it's divisible by three and then we can print Fizz and then if we copy this exact structure down and change this to a five to check if it's divisible by five then we can print out buzz and in the worst case scenario where none of them get applied then we can simply print I to the screen and actually there's no point in starting at zero because normally these start at one so we'll just do one and we can make it 15 by making it less than or equal to so instead of before it was actually going from 0 to 14 now it's going from 1 to 15 and they will tell you this in the interview they might say counting from 1 to 100 print out all of the Fizz buzzers so let's run the code and see what's going on 1 2 fizz fizz is actually three so three is divisible by three then you have four and then five is divisible by five you get buzz and six goes into three so you get Fizz nine you get Fizz because it's divisible by three then 10 / by 5 gives you buzz 11 12 goes into three so you've got Fizz and finally when you hit 15 it goes into three and goes into five so we get Fizz buzz and the way to increase this to 100 is by simply changing this to 100 if you need to and you can scroll through the entire input and you can see all the history if you wanted to make this slightly efficient what you could actually do is store the booing values for these calculations before you can store the values for these calculations before so we can say Bo 3 div equals false and bull 5 div equals false and what we can do at the start of each of the for Loop is we can say three div equals this value and five div also equals this value and then every time we find a calculation for three or calculation for five we can replace it with either three div or five div so let's change this one here and this one here and our five here and here and because these are values now we want to actually store them as true or falses so we don't need to check if they're equal to zero so we can just remove them so we can say if three div and five div are both true and they'll only be true if these two are both zero now if we run the code and just make it 15 again just just we have a Shor output you can see that our code is exactly the same the reason why this is more efficient is we're only doing this calculation twice whereas before we were doing it twice for three and twice for five now we're doing it once storing it and then making use of it this is a lot more memory efficient than having to calculate it every single time it computes a lot faster and it's better for readability if the rules of the game happen to change and this was divisible by four or six then you could just change it very easily whereas in the previous example you would have to change it in every single case in C when you're constructing strings that have backslashes you're going to need to use double backslash and the reason for this is the first backslash is an indication that it's actually going to be an escape character you're going to put an escape character in and then put the character that you want to display and the reason for that is they've chose backslash as the designated character so so you can use backs slash and then a backs slash to show one backslash only and what this means is it will use the first backs slash as a reference so it knows that it's going to process the next character as an escape character I want these Escape characters are you can have things like T for tab n for new line and you can even use speech marks because if you outputting some dialogue and you wanted to say something like this he said and then you added your own quote in there if you want to put something in quotes then you can't because the speech mark dictates that this is the end of the string literal that's why it's gotting it off like this and then now it's not recognizing that something is just wrote here and what it's actually doing is you've got two strings specified one that says he said space and one that's just empty and then you just have this something that's just in the middle of course we actually want to insert the speech marks within another pair of speech marks this is where the backslash comes in so you can insert a backslash before here and this is now acceptable and the same thing with the normal backslash because the backslash character is also going to be the Escape character then you need a double backslash so then that equals to a single backslash when you print it out let's Show an example so we have C colon SL slash which will return us back a single slash but visually right now it's a double slash but when it gets processed or outputed to the screen you'll see that it's a single slash so this common example is when you're constructing a path together and you want to use backs slashes to denote the different directories so let's output this to the screen and see what happens and as you can see we have a single backslash because of the Escape character we don't see both of them and if we print the Spree out to the screen just to show you that as well then we can see that there's only the speech marks around the something and we don't have the backslash you can tell when an escape character is being used because it goes a slight hint of yellow instead of the normal color for a string so now that we've worked out that this is how this works let's see a way that we can undo this to make it easier for us so you've used the dollar sign for string interpolation and you've used the plus just to concatenate two variables together and just as a quick example it looked something like this your name is and then the name variable and using the plus you would say your name is followed by a space and the quotation marks and do plus name that's fine and now we have another one so similar to how we placed a dollar sign before the speech marks we have a Verbatim identifier and what this means because it says verbatim it just means whatever you see is whatever happens so let's try and Define this path a slightly different way but still containing the exact same information that you see when you print out to the screen so let's have a look we can reassign the path value and just before the speech marks we can put it at symbol and this at symbol means it will actually negate all of the Escape characters it will process a single backslash as a single backslash let's take this line of code and place inside here now what you see is that tint of yellow is no longer there so if we print this past to the screen let's see what happens we actually get the double backslash because it's ignoring all the Escape characters which means if we take them all out this actually looks exactly how we want and you don't have to worry about the Escape characters there you go these two are identical even though one is being displayed using Escape characters and ones using the verbatim identifier please note that if you're going to use the back slash n for example and I'll just demonstrate at the end of this new line test and if we run that code again you'll see that it's printed the path on one line the back sln has made it go on to the next line and now it's printing new line test on a dedicated line that's fine the problem is if you use a back sln or a back SLT or any of these Escape characters during the at symbol then it's going to process it as literal characters which means you can't mix a back n with an at symbol AS this is just taking the text verbatim so if we try to run the code now you'll see the back sln will actually appear in the code if you wanted to do this then maybe you could remove the back slash n and add a plus at the end and then make another string that just has a back sln and then this string will not be processed as a Verbatim string because we don't have the at symbol right before it so then we can have the exact same thing here just to show you this so now these two are identical again just as shown here and as shown here the difference being that we can't specify a back sln in the same string we actually have to concatenate them together because of the verbatim identifier so let's have a look at speech marks so if we have a string name and we can make this equal to hello and then someone and we said before that we have to use the backslash so we can activate the Escape characters and that will work and if we just print that to the screen to make sure then we get hello someone in the speech marks if we add the verbatim identify at the start then we see we've got an error it's trying to process it differently this is a little Quirk with the verbatim identifier if you want to insert a speech marks you actually want a double speech mark on either side the double speech marks will get processed as a single speech mark because it's within a speech mark the verbatim identifier needs to know that you're specifying a speech mark and this acts as a same reason why you have a backslash here it's slightly quirky doing it this way but it still works as per you expect and when you're specifying something like name and we can say hello someone so let's print name to the screen and make sure it works in this case we don't actually need to specify any sort of Escape character because the quotation mark is a separate character to the speech mark and it doesn't interrupt anything by placing a quotation mark inside the string just represents that as its own character let's run that and make sure it works there you go so just as a quick recap Escape characters are very essential because we can use things like back SLT to give us a tab character in our console output this can be very helpful cuz you can almost mimic the use of columns inside our console output you'll notice that back sln is used quite a lot in the console output so you can separate lines without having to use multiple console right lines if you have a single backslash you can't have it on its own if the string is not a Verbatim string you have to pair it with another character otherwise you will get a syntax error if you want to use the verbatim string then you can put an at symbol before the string definition and then it will ignore all of the Escape characters for example using back sln within these speech marks will mean that the back SL n will literally be printed to the screen and you won't get the new line functionality that back sln provides when you want to print speech marks of the screen using the verbatim identifier you have to use a double speech marks in order for it to show up and as you can see it slightly goes yellow and that's the similar notation as using Escape character when you don't have an verbatim string if you're using other characters that are similar to a speech mark like a quotation mark because this doesn't interrupt the syntax of the language then this is fine because a character can just be inside a string and to the compiler this is just a character even though they are very similar the quotation mark doesn't affect the speech mark the most common approach for outputting values to the console is by having this format you type something in as a static string and then you add a variable to it but when you're doing long sentences this format can get messy quite quickly so this will just output both of these on separate lines the name followed by the name variable and the age followed by the age variable I just have a console right line to split up these two sections just so you can see it visually in the console so if we run this code you can see that both the outputs are exactly the same and the reason why is we can use this back sln what this back sln is doing is inserting a new line character just where my cursor is here which is forcing The Edge to jump onto the next line the reason why this is a slightly different shade to the age text is because it's an Escape character back sln means new line we'll explain this in a further video in this section so don't worry about that just know that it means that it produces a new line so as you can see since we're adding the name followed by the name and then the age followed by the ede then it's getting a bit long and a little bit tedious it's not too bad in this case because we're not really printing out a sentence we're just going straight to another line but let's see what this is going to look like if we start dealing with multiple pits of data your name is followed by the name and then we can add a comma and your age is and then add the age and as you can see while we're structuring a sentence then it gets a little bit long we have to remember to put in the spaces otherwise our code is going to look funky when we print out to the screen and the reason for that is there's no spaces between the name and the age variables so let's put them back in and make sure the output looks all right now that the output looks like this let's explore composite formatting and what this means is we can get rid of all of these plus symbols and replace it with curly braces so let's actually output this string again but just output it completely static your name is abber and your age is 23 and now if we've run this you'll see that both outputs are identical this is because I know the values for the string variables up here and I can input it straight into here so now that we know what our sentence is going to be we don't need to add any pluses what we do need to do is remove our variables so in the case of this sentence our name variable is here and our age variable is here so we can replace this with this curly brace notation we can have curly BRAC and then we want to start this value at zero throughout the string you want to have these values starting from zero and going up incrementally from left to right so our next variable would be our 23 and we can store it like this now that it's got your name zero and your age one let's see what happens when you output it then we just get this and this is very confusing that's because we're not done yet so now that we've got our string typed in we can actually place a comma in here and now it lets us put any object in and any object could be a string an in a double or any data type so we want to insert the values inside here going from left to right so our name is first and then we do a comma and we type in Age and what this now says is the name will get replaced by the curly brace zero and the age will get replaced by the curly brace one so now if we run the code let's see what happens and now you'll see that the output is exactly the same and now look at the difference between these two lines you'll see that these multiple amount of pluses are not confusing and let's say you forget this one then you're going to get a syntax error and it's a bit frustrating to keep on typing when you're trying to join things together now we can clearly see that this flaw is like a sentence and this space here looks very unnatural but this space here looks like it's part of the sentence which makes our code a bit more complete and the same goes if you want to print something like this and let's convert this one so if we copy this line down into here and we just remove the spaces then it can look something like this name followed by the name we don't actually need this space here because we're going to be going into a brake line we can replace our name with curly braces zero and our age with curly braces one and then straight after we can type name and age and if we output this we'll see it's exactly the same there we go so just a quick recap print ing strings and any other variables to the screen has been normally achieved by doing a string followed by a plus and then adding another variable to it adding more than one can be a little bit complicated and hard to track of all the spaces that you're going to put in and you might accidentally miss one of them like this one here or this one here are very crucial to the output if you miss this one then it's going to say is followed by the name all together with no space we then introduce composite format in which lets us use this notation of curly brace Z and curly brace one to give us the ability to store some variables outside of the string and then insert them in dynamically we took both of these examples and made them down here using composite forming so let's explore a new method of concatenation that makes this look a lot better the reason why this is an issue is you have spaces in here and sometimes you might forget these spaces and it could mess up your program this string here looks very unnatural because you're forcing the space but when you run it you'll see that it is actually what you expect the spaces are complete and it makes perfect sense but when you're writing it it kind of looks a little bit stupid because you're forcing the space and then adding a plus and then the name and then another plus and then another static string and this just get a little bit long to type it's fine when you have a smaller sentence like this but when the program starts to grow it could be a little bit problematic and you'll have a lot of syntax errors when you forget to type in all the pluses locally this can be fixed let's duplicate this line down and let's see what we can do so we have this thing called string interpolation and it uses a dollar sign as a reference we can place the dollar sign before the quotation marks and then what you can do is you can actually keep this as one big sentence so let's remove all of the values and have it like this so now of course this actually doesn't print our variables because we've just replaced it with text so if we just run this then it's completely messed up because now we're not using our variables and this can be easily fixed because we've used our dollar sign now we can actually wrap our variables in this curly brace and now you can see it's went white if I double click on it you can see that it's referencing the variable wrapping the variables in the curly brace means that they can actually be processed variables even though they are still within the speech marks please do not remove the dollar sign because now this will be interpreted as string text as you can see here putting a dollar sign at the start will make into string interpolation and then we get the ability to have our brackets this can make string concatenation very easy to do because you don't have to worry about all the pluses and adding them together and don't have to worry about the spaces as well this looks more like a natural sentence and what you can do for practice is you can actually just type out the sentence your name is AB your age is 23 and then from there you can actually just break down the variables and know that you'll need one here so you can replace that with name and then you'll know you'll need one here so you can replace that one with age and then you can place the dollar sign right at the end and then there you go you have your solution this method means that it's a lot cleaner to read easier to maintain and make changes in the future and that's the whole point of programming if your code base is very difficult to go around and understand what's going on and potentially make changes in the future then you've already made a bad step and you don't want to get into these nasty habits it's fine if you're just going to have something like this where it's not really complicated at all a string plus another string that's quite simple and that's fine you don't have to go the extra effort to put in the dollar sign and wrap it around in the curly braces even though I personally still would because in my personal opinion this looks a lot better than having it like that you can see that it's a lot neater it takes up less code and you can see visually that you're using a specific variable and you don't have to worry too much about the spaces because this looks like a real sentence explore another method of string concatenation which is the idea of taking strings or objects and add them together to form a sentence of sorts we can say your name is followed by a space and then add the name followed by a space add your ages and then add the actual age variable and we can also write the exact same line using string interpolation or composite formatting just like this and like this we can specify the dollar symbol and put our variable in the bracket which is shown here and here and for the composite formatting we can take the content where our variable would go and replace it with incremental numbers 0 and one wrapped around in a curly brace and then specify in the correct order zero takes a value of name and one one takes a value of age if we run this code you'll see that the outputs are identical so let's explore this other method we have a string test for example and then inside the string Library we have this function called concat and it can taking any amount of parameters that we want to give it so we could say your name is space and the quotation marks and then we can add a comma and then we can say we want to add the name and then another comma and we want to add and your ages and the speech marks add a comma add the age variable and that's it and we could just use CW tab tab and type in test and let's run it and see what happens and now as you can see we get the exact same output and because this just returns us back with a string we can also just take this entire line and paste it straight into the console right line you don't necessarily have to store it but you can if you want to and there you go all methods produce the same output another way you can use this concap function is by giving it an array we haven't covered arrays so far so I'm just going to show you this for demonstration purposes don't worry about understanding it so just a quick explanation arrays are just ways of storing multiple of the same data type so if we have these three names inside our names we can actually use the console to print them all out so we can say string. concat and then we can concut the names together which will just add all of these three together now the problem is when you've run it you'll see this stuck together so what you could do is just add a space between them and as you can see this is getting a little bit tedious now there's other methods that we can use to concat some arrays together and I'll show you that in the next section but for now don't worry about it this is concentrating on the string concat function and we'll just demonstrate that again so if we run the line of code we can see that they're all the same so now that you have four different methods of printing out exactly the same information you might be asking yourself what's the best method I personally prefer to use the string interpolation because with this one you can easily miss the spaces and you could produce a bad output and it might be stuck together it's fine when you can see the lines right in front of you and you can easily identify the spaces but when you're adding about 10 variables together then it could be a problem the reason why I like string interpolation using the dollar signs and the variables in the curly braces is that you don't have to rely on missing out spaces because it actually forms a sentence and you just replace the use with your variable composite formatting which is this one is very efficient and very nice to look at because it allows you to specify the sentence and then plug in the variables after the only problem with this is if you were to change this value in the future or to change a sentence you have to make sure that the numbers add up just like in the first example if you only have a short sentence then this isn't really an issue since you can see it all visually and you also got to realize that these need to be in the right order because if you put Age first then it's going to put age in this one and name in the second one and that's going to be problematic cuz it now mess up the sentence using string interpolation you don't actually have to worry about anything because if you wanted to change this to say your age is then you simply just do this and that's very easy to do because in this case you'd say your age is and then you'd have to change a string and then now that this is zero we need to change this from being age and this one to be name whereas in the first example you could just easily change the value in the curly braces instead of changing this reference and the end reference cona is not widely used just because you have all of these methods available where you can easily add stuff together but there could be user cases later on down the line where users just so it's a bit more obvious and it helps the readability of your code and maintain within a big project or just on your personal projects when you're looking back at your previous code when you create and initialize a string variable you might want to give it the value of an empty quotes and this will just default the value to essentially nothing you're giving it a value but at the same time the value doesn't actually contain any sort of characters if we print this out to the screen then you won't really see anything this video is going to focus on string.empty and string.empty will actually just represent these quotation marks string. empty will represent these speech marks so what we can do is we can type in string using a DOT and then we can type in empty just like that we've initialized our string name to a value of empty now this isn't necessarily used when you're declaring and initializing it because this is almost identical to just defining a string on its own main reason why this is used let's say we actually ask the user to input their name so we can say a console. write enter your name and then we can take this string variable move it down use an alt and then arrow keys and remove this and let's initialize it to a console.readline to read in the value from the console and now what we can do is using our is string interpolation method that we just learned we can print to the user your name is and then the name in The Curly braces now let's just see what happens so let's actually type our name in Abba and it says your name is ABBA but what if the user just types in nothing and just presses enter Then it still says your name is blank now let's see what we can do here we don't necessarily want to say your name is blank we want to check what this value is so we can say if the name is not equal to empty quotation marks then we can output your name is and then then else we can say name is empty and then if we run it now and press enter it says name is empty so we can use string. empty instead of these quotation marks this looks a lot better when you're trying to compare it AB your name is Aba and then when we press enter it says name is empty this just helps to keep your code a lot tidier just so you don't have to write the two quotes if you accidentally put a space in there now your if statement is incorrect if you always use string. empty then it just helps you to make sure that your code is going to be maintainable and readable in the future reading string.empty gives you a better representation of what's going on instead of two open quotes if there is a situation where you want to check if one string equals another string then you can do the following if message equals equals compare then we can print out same and then else we can print out different and as we can see here they both have a capital H and they both say hello so they should be identical let's run the code and find out so they say same which is exactly what we'd expect so we have another method of being able to do this so even though we can apply equals equals to two strings it's normally better practice to use do equals and then place the other string inside the brackets so you're saying if message equals compare now if you run the code you'll see that it's the same output in certain circumstances where you want to ask what the user has entered enter your name and then we can use a string name equals console. readline we can say if the name does not equal to empty strings then from there what we can do is type in your name is plus name and then we get some output your name is abber but since we're checking if it's not equal to that that means they've entered something in let's see if there's another way that we can actually write this so if we just duplicate it and comment it out so we got it for reference so what we want to do is we're checking if name is not equal to empty quotes so we can say name do equals empty quotes but what this is telling us if the name equals empty quotes then we should do this so then what we can do when we learn about the if statements is we can use the not operator and we can say if the name not equals to empty quotes then we proceed with this line L we can just say invalid name input let's run that and see what happens to type in AB then it passes fine and if we type in nothing then we get an invalid name input the reason why equals equals and the do equals function are different is because lower level using equals equals will actually compare the reference in the memory and the reference in the memory is what's used up when you actually create these variables so what this is doing is it's comparing the value that's actually stored in memory to the other one that's stored in memory now the problem is when it comes to something like arrays where you actually have the same value but they're slightly different let me demonstrate so I'm just going to use this code because we haven't covered arrays yet so I'm just showing you an example if we have a chart array that literally says hello and then we can use this line of code to join them together but this is actually an object instead of a string but if you see what we can do in the if statement we can say save the message which is equal to hello we can use message. equals and we got the new compare and this is actually an object so now we're comparing a string with an object and generically speaking an object can hold any sort of value because all of these variables that are strings ins double Etc they're all derived from something called an object which is just a very generic way of storing information so since these two data types are little bit different they still evaluate to the same thing what the equals function is doing is actually checking the literal values of the variables instead of checking the values that are held inside the memory address location and the difference here is even though we have a character array that is giving us the values hello and our string is also given us the value of hello if we run this line of core that uses do equals then you'll actually see that the second same actually represents the bottom if statement so what that's doing is it's actually giving us back the comparison saying that it's true and it is indeed true because hello is literally equal to hello but if you were to use the double equals then what you'll realize when you run the code is now it will say it's different because what it's doing now is it's taking a string object and comparing it to an object and they are not different because of their memory and that's what the equals equals is comparing it's not only comparing the value it's comparing the memory address location and that's going to going be vastly confusing because you don't want to hit these situations so it's always best to use the equals function because the equals function is concerned about the values rather than where they are in your memory I hope that made sense and it wasn't just confusing but basically when you use equals equals it checks the values that are actually wrot in your computer's memory instead of the value itself it will do both it will check the memory and check the value whereas when you use do equals it is only concerned about about the values and that's all that matters when we're doing an if statement like this we're checking if they're both the same so it shouldn't really matter how and where they are stored the only thing that matters is the values contained within the variable we're only caring about the values and not where they're stored so when we have a string variable defined in C we have it like this and when we print it out to the console we get the entire string being displayed but what if you want to return the first element back not the rest then what are your options so in the later video in the course we covered the substring function and technically you could go from the first character till the second character and you will just get C back so that's index zero till index one and you'll get the C back now the problem with that is that's an extra function call or something that should be quite simple and it is a message is a string and strings tend to be an array of characters which is similar to this we haven't learned about arrays so far and we'll cover that in the next section but what an array essentially is is it lets you store multiple of that data type so we could have a chart array that holds exactly the same value and each position will hold each one of these characters and the reason why I'm mentioning this is because with strings you can use the square bracket notation so if you add some square brackets at the end it says here it returns back a Char and it takes in an index gets the CH object at the specified position in the current string object so if we use message zero you can see that returns back with a ch ch right here gets the CH object so we can call this on a string and it can return us back with a character because like I said with the array of characters that's essentially what a string is each one of these is just its own independent character and a string lets you pair them all together so if we print this out then we should get C because it's zero based so if we copy this down and use one 2 and three then what should we get we get C then we get actually nothing technically because it's a space character and then the third character which is the fourth in the list because it's zerob based is going to be our I so let's just print this out to the screen and see what happens there we go so even though we don't see it visually there's actually a space character right there and that's the third character in The List which is right here so of course we don't tend to know how long the string is unless we can see it visually and if you were to reference one of these values and the string is not actually that long then you have a problem let's demonstrate if we have the string just called C and let's comment out the rest then that's only two characters so only zero and one will be applicable these two will return back something let's have a look and see what happens so the first character and the second character will run fine and let's put a console read line in there just to break it up so the other code doesn't run yet if we run the code we get our C and that's the max length of our string so so far it's zero and one now if we press enter let's see what happens we get an index out of range exception index was outside the bounds of the array and the reason for that is we only have two characters inside our message and we're trying to display the third and the fourth this is problematic because we literally don't have any of them characters to display so what we can do instead is actually write ourselves a little Loop to go through the entire string and return us back all of these character positions instead of us just get ing how long the string is so if we return this string back to normal and then just after this little section we can write a for Loop in I equals 0 and I is less than message and then we have access to dot length this gets the number of characters in the current string so we don't have to worry about the maximum length in the square brackets we can always rely on do length because we don't have to keep track of it and the language can know that for us and give us the value in this case we're going from zero to whatever the length is these characters are and then in here we can actually just console right line and we can do the same notation we did here we're say we want to print the message but not only the message we want to print the index and the index is going to be I in this case because we start at zero since it's zero based and then we're going to the last character so let's print this and see what happens so now we get C Is Awesome from here down to the bottom c is awesome print on every single line and that's a little bit annoying to read so what we could do is just change this to a console right and maybe we can just comment this section out just so we can see this properly there we go so we get c is awesome and because it's a console right it's right in them all next to each other and they're being printed out one by one let's add a cool little effect that can demonstrate you for now so inside the system. threading Library we have this sleep function so what we can do is we can add another using command system do threading we already have threading do tasks in there but the function that we need is inside the threading Library so there's two ways we can write this we can actually write everything by hand like this do sleep or you could just remove the system do threading because we've added it at the Top If you don't want to add it at the top that's not really a problem you can just include it straight into here adding it at the top will include it within the entire project but if you're only going to use it once or twice then sometimes it's better to just include it straight into here because it'll make your overall program size a lot smaller so let's just keep it in so we can make our code a bit more readable so we have thread. sleep and what this will do is it will suspend the current thread for a specified number of milliseconds there's a th000 milliseconds in 1 second so what we can do in here and we're trying to mimic a typewriter effect so we can say something like 200 which will be roughly a quarter of a second so if we've run the code now let's see what happens so we get this cool effect where after it prints out each of the characters characters it will print out the next character only after it's been asleep for a quarter of a second and that looks kind of cool if you wanted to speed it up you could just decrease this number there you go of course if you make it too low then it might be too fast for you to actually acknowledge what's happening and if you also make it too slow then it's just going to take too long to turn off and at that point you can use control+ C on your keyboard or use the stop button at the top to terminate the program okay so let's have a look at another thing that we can do with this so maybe we can make this 100 for now in the previous videos we've used a function called contains and let's say we're just checking if it Con turns C and we know it does because we can see it visually let's run the code and we see we have true being printed and the reason why true is actually on the same line as c is awesome is because we're using console. right here so it's actually not made a new line character just after the E so when it's printing true it prints it straight after that so what we can do do to fix that is just place a new line character in here using console. readline and we can just drop this a little bit lower to 50 there we go so we have true and what we can do with this is we can actually make our own little version of the contains function let's demonstrate so if we make this exact for loop again in I equals z i is less than the message. length and i++ so first let's kind of understand what's going on with this function returns a value indicating whether a specified substring occurs with in this string and what that means is it will return a Boolean for us if C is inside our message then this will return back true and we know this is true because we just outputed to the screen and we can see this visually so what we need to do is we need to Loop through our message and try and figure out if we can find C inside our message and then we can give back a value of true so maybe we can do a bu contains equal false and the reason why we initial it to false and the reason why we initialize it to false is because we want to set it up telling that we haven't found it and then inside the for Loop if we find it then we can set it to True let's have a look so after the for Loop we can print contains of the screen and then inside the for Loop what we can do as we've seen here it returns back every single character so you'll get back C sharp then the space then I then s and so on and so forth and what we want to do is we want to go through each of the characters and then just ask if the variable is equal to C if C is equal to C then we can assign this to true and then go through if hashtag is equal to C if space is equal to C and so on and so forth so we can write a if statement here that says message square bracket I is equal to equal to apostrophe C and the reason why it's an apostrophe is because this is a character and this also returns us back with a character so we need to compare them both like that if we use a string in here then it might complain that we're trying to convert between a chart and a string and it won't let let you do the equals equals operator between two different variables maybe what we can do instead is to follow the approach that we used before and use the equals function and place our C inside here so if the character that we're currently up to inside the for Loop is equal to our C which is what we want to search for then we can set our contains variable equal to true we don't need to write an lse statement in here to set our contains to false because we've already gave it a value at the start if we didn't have this value then it'll be beneficial to do this but since we have it then we can remove this other path and we don't exactly need it so let's have a look and see if this works perfect it says true maybe we can change this character to something like air make sure this works which it does as well so perfect so now we've made our own mini little contains function inside here and we can also use the C library one but the purpose of this exercise was just to show you how we can iterate through a string variable and and then decide what each of the characters can be equal to and then we can decide if they're equal to another one and then let the user know that we found a match for their search term so far in the course we've covered the equals function and the contains function when you're searching through strings or trying to find values let's have a look at a method that makes sure a string is valid before we can process information on it so in this quick example we have a name output we're reading the value into a string name and then we simp complet output it to the screen if we run the code and just press enter then it says your name is blank and we don't really want that because we want to check if your name is equal to something before we continue so let's look at some methods so we have if the name is not equal to nothing and then let's just print zero to the screen and that's one of the methods and we can say if name is not equals two quotation marks then let's print out number one so what what this is doing is checking if the name is not equal to empty quotes and then this is doing exactly the same thing except we're using the equals method and let's just run the code and press enter and you can see the zero or the one doesn't appear because it's detecting that it contains nothing so if we type in a real value we can see Zero and one coming up so these are both valid ways of checking if the string is not empty so let's look at a third one and this one is actually very important for reasons I'll explain in a second so inside our string Library we have is null or empty so we place our name inside here and let's see what this says now indicates whether the specified string is null or it's an empty string so this can be very effective so what this reads now is if the string is null or empty then we print a value but we want it to be not null or empty because it wants to have some contents so if we type a value in again you'll see now we get all three numbers and what them three numbers mean is that it's past all of these checks and each of these checks just ensures that the value has got something inside and that's fine but it can be slightly problematic for this reason using this method and this method are fine in some cases except as it says here it checks if the string is null and null means it doesn't have a value but it just has nothing instead of something let me demonstrate if we assign the value of empty quotation marks this actually has a value but the contents is empty but it's still a string as it comes up in here if we assign this the value of null then it's just a keyw that we can use to denote that this literally has no contents it's not that it has an empty string CU an empty string is still actually a string whereas a null it just means the variable is blank now this is where the issue arises if we try and call a method on something that's null Watch What Happens we actually get an exception and our program just crashes you can't run any code on something if that variable is actually defined as null it doesn't mind if you check the value of it but if you try and run a function then you've got a problem so if we comment this line out this ensures everything it ensures it's null or it's empty and this is the belt and braces option because if it's null we don't actually get an exception when we try and run this code as follows we get the zero showing up because our variable has something that's not speech marks and it's actually null so we want to avoid this option as well and also avoid this option in case our string is actually genuinely null using is null or empty we'll check both for the value of null which it is right now and if it's got empty quotes EG the value is empty so if we just run this again and have these two paths commented out we can see that two is not appearing if we change this back to our console readline and we try and do it then we get our number two because it's validated that this string variable is got something inside it and the variable is not actually no this is a very good way of being able to make sure that your program doesn't get exceptions as with calling these equals if you want to call equals then call it inside here you can check if that variable equals something by simply placing that if statement in inside here after you validated if the name variable actually has some contents if it's null or it's empty running equals on it will just break the code further and you don't need to check if it's equal to Something in here maybe you were checking if the value is equal to abber or something along them lines and now if we run it again we actually get the output correct it's best to Nest them like this because if you run this function on something that's null it's actually really safe but as you saw previously if you run a function on something that's null then you're going to get a null reference exception and your program will close down and break you want to avoid exceptions at all cost so nesting it inside it is null Remy check will be perfect for your code it improves the stab ability of your program to ensure that exceptions don't happen so in this exercise I want you to ask the user to input any message and then I want you to print the message in Order character by character and then also print it in reverse character by character let's get started so we could just have a console right line but let's change it to a right and just say enter your message callon and then speech marks and then just have a string message equals console. readline perfect so in order to be able to Loop through the string message we need to have a for Loop if you remember from our previous videos we can have this string variable followed by a square bracket and then and then we can have an index inside and that will print us back any sort of index based on that position so if we just have this is a test then it's prob print as the T because that's the first index and so on and so forth so what we can do with this information is take what we can do with the string index and then also use the property which is length and then use these two values to be able to process this is a test so we have the first character square bracket 0 and the last character is at length 14 so our message variable now contains 14 characters obviously When I close the program then that value is lost and I have to re-enter it but because of that exact reason we would always use do length because we never know how long the user's input is going to be so we can have a for Loop so we can say 4 into I equal 0 I is less than and we can use the message. length here and then we can say I ++ so you want to start at zero because our first index position is inde Z and we want to go from the index zero all the way to the length now in that example I just printed out 14 for the length but you got to realize is there might be 14 positions but there's only 13 indexes so it's not actually 13 index it's just up to 13 when you start at zero going from 0 to 13 gives you 14 positions so when we're saying 0 is less than the message length then that will actually take us from 0 to 13 instead of 0 to 14 if we made this greater than or equal to and change this to a one for example then that's going to go from 1 to 14 and first we're going to miss out the first character and we're actually going to go one over the message length so you always want to start from zero if we're going through the entire string so this will go from 0 to 13 and then here we can just have a console right line and just print message square bracket I and then just for the time being we can comment out these lines just so it doesn't saturate the output so let's run this Cod code and see what happens this is a test and then we get them all on separate lines maybe we can just use a console. right instead so we get each character on the same line instead of a new line character being outputed at the end of each of the lines so we can say this is a test again and there we go we get this as a test outputed as well so now that we've printed that in order let's see how we can print it in reverse so just a quick little tip throughout this C I've been quite hard on you I've made you WR the for Loop out exactly the way it should be but all done manually this is so you can get used to the syntax and after a while once you understand exactly what to do then what you can do is when you type in the four you can see that it says there's a for snippet tab twice to insert the for snippet and we can do that now and it actually gives you a little bit of an output you can see these sections that have been highlighted the reason they're highlighted is once you're done with one section you can actually press Tab and it'll jump to the next one so now my cursor is jumped on the length and we can type in message. length if I press tab again then it'll just keep cycling through them until we're done and we can press Escape upon pressing escape then it gets out of the little message and there we go we've now just defined a really quick for Loop please only use this once you're comfortable writing for loops and don't use them immediately because you might get stuck on what to do and how to do it so it's best to always write the for Loop syntax out from scratch so you can get used to the three different sections so this is actually a for Loop that goes forwards it's going from 0 to 13 but what we actually want to do now is go from 13 to 0er so let's actually change this for Loop completely and we can do our little shortcut again so if we do four and then we don't actually want to start on the value is zero we want to start on message. length and then you want to minus one and just as we said here we never actually want to get to the length because we want to go from 0 to 13 so if we want to go backwards we want to go from 13 to zero and the only way that we can get this 13 is by getting the 14 value which is message. length and simply minusing one so now that we've got our first variable which is in I equal message length minus one which will give us the 13 we want to go from I and instead of less than it's going to be greater than or equal to and then we actually want to change it to a zero because we actually want to stop at zero in this case and then we don't want to use I ++ because if we start at 13 we want to go down in one instead of up in one then we can simply just do minus minus we can take this exact line and print it out to the screen and if we just print something small in between like a hyphen just to separate the two outputs and let's see what happens test there we go so we have test and then t s e and t is now in Reverse but now you might be wondering if we had a shortcut for the four what what's this for with an additional R Cordes n it for a reverse for Loop so if you tap tab twice you can see that we have exactly the same format in I equals something minus one which we have right here and then we have I is greater than or equal to zero as is we have here and then we have IUS minus just like here so we can literally just change this into message do length and then these two now are exactly the same so just copying this down we'll get us exactly what we need but obviously we just wrote this I just wanted to show you the shortcut so let's try it with a longer string this is a test there you go and if you wanted to you could just print these on separate lines so you can just change this into a right line for example and have it like that it doesn't really matter the rest is up to you but the task is just so you can print it one way and then print it the other way I realized that what you can also do is just simply print a console right line and have message in there and just get rid of this completely and the output will still look exactly the same there you go and the reason why I told you to write the for Loop is not because it'll be easier if you do this it's more for your Educational Learning purposes having more practice to how to iterate a string variable is very helpful for the future and you can understand it fully if you just print out to the screen then you're not learning anything extra you're just applying what you already know so let's just have a quick recap we ask the user to enter the message we STW it into a string variable and then Iden demonstrated that you could use the square brackets to Output the first index then you can output the length of the entire variable using a follow you can go from zero to message length which will give us from indexes zero up until 13 in this case and then we can go through i++ incremen in one and then we can have a console right which will just print out message index I for the index that we're currently up to and then we break it off with a console right line just in the middle because these are printing on the same line so we need to insert a new line character at the end after we've done that what we can do now is print it in reverse and now we can do exactly the same thing except from 0 to 13 we go from 13 to zero so we start at the message length minus one because the length was 14 and now we minus one to get to 13 and we're going from I is greater than or equal to zero because that's the value that we want to stop at and then we can do I minus minus if we were to take out this equals operator let's see what happens test and now we're actually missing the last character because what we've done is we've actually went from 13 to 1 instead of 13 to 0o so let's put that back in and make sure it works and then we have t set for test and then we're outputting the exact same thing in both for Loops because we're simply just printing the character that we're currently up to and because this for Loop starts at zero and this for Loop starts at the length minus one then they outputting the same values or what it appears to be the same values it's just starting at different indexes in this exercise we're going to be building some sort of a password validator this can be present in something like a register form where you ask the user to enter their password and then enter it again to make sure that they've entered it correctly so you want to ask user to enter their password in twice and store them both check if they both contain something if they do we can print out password match if they don't passwords do not match and if they both contain nothing then you want to Output please enter a password so let's get started first we can have have a console console right we can have enter password string password equals console. readline and then we can just copy these two lines down using contrl D and then we can have a password C for password confirmation and we can say enter password again and let's just print these out to the screen just to make sure we know what's going on just like so so we can have abber and then abber again so now we have both AB stored and that's fine so let's see what we can do now we need to check if they both contain something so what are the different ways that we can do this so we can have if password do equals and then we can make it equals to string. empty and because we want to check if it's not empty then we can simply place the not operator right at the start and then we can join them with another one not password. equals and then exactly the same thing string. empty but in this case we don't want to use password we want to use password C there we go so if we've came into here then that means they must have entered something so let's just quickly do our exit path which is if they're empty please enter a password so we can say else and we don't need a condition here because if this were to fail then it has to mean that their passwords empty so we can have a console. right line and we can just do please enter a password and let's just test if this path works first and we just press enter twice and we get please enter a password and maybe if we typee something in for both and then we get nothing because it's actually came to here now perfect so if we come through and we can say password equals equals password C or we could use the equals function and we can say password. equals and then password C and if they both equal to each other then we can print out passwords match there we go and if that were to fail then we can print out passwords do not match here we go let's run that let's find out ABA and ABA and we get passwords match and if we try ABA and ab two is and then we get passwords do not match so what are some other ways that we can do this you can structure this completely differently right now we're doing both checks in one single if statement and we can actually split this up into two and then provide a different error message so right now this ISS please enter a password you might have entered the second one but not have entered the first one or vice versa but it doesn't matter because you have to enter both of them in order to pass this validation check so what you could do instead is actually put another if statement inside and paste this one inside here and then just keep these as two separate if statements and then you can actually provide different error messages so let's Nest this in one deeper so we can say if the password is not equal to empty and if this returns back true then this variable has something inside it and then once we go inside these curly braces we get another check and if the password C is not equal to nothing then that means if we've came in here then we pass both of these validation checks and both of them contain something and then we can proceed to check the variables so what you can do in the first L statement is you can say please enter a password but on the second one so just after this curly brace we can have another L statement or we can say please enter a password confirmation so I know that was a bit quick so let's just have a quick recap so we can have one if statement that processes the first password that you type in and if this is empty then it says please enter a password and if it's not empty then it'll go inside this curly brace hit the first line and check if the password confirmation is not empty if it is empty then it'll say please enter a password confirmation if both of these return back true then it will go inside the success path in which it will actually check if password is equal to the password confirmation and we can say the passwords match or if they don't equal to each other we can say the passwords do not match let's run that and see what we get so if we type something in for the second one but not the first one so for the first one we just press enter and then let's type something in for the second one and it says please enter a password and then if we run that and do the complete opposite type in p and then press enter for the second one then it says please enter a password confirmation so you can see immediately what we can do is provide a different error message for different situations if you include these both in one line then you can only give out more of a generic error message this is similar for when you go to login and when you get your password or email wrong it doesn't say which one you've got wrong it just says them generically which one you've got wrong it says invalid credentials or invalid username or email it will say them generically like invalid username or password but it won't tell you which one it is because hackers can exploit this and you don't want to be doing this but in the case of a password confirmation and this is just for a register form then it's not exactly the worst thing to do this because sometimes what you'll see is the text boxes might go red to indicate that they're both not equal to each other and this is fine on registration but it's not fine on the login what we can also do in here once we've checked if they're both not equal to something we can actually just validate how long the string needs to be we can have if password. length and let's say you had a restriction and it can only be over six characters and we can say six and password c.length is greater than or equal to 6 and once it passes all three of these checks then we can check if they're equal to each other if they got something inside and if they've got something inside and if they've got both the length is greater than or equal to six then we can check it so we can have something like password and then password and then this returns back with password matched if we have something like abber then it's actually returns back nothing because we don't have an else for this specific bracket so we can say else conso right line please enter six or more characters so if we type in Alit twice then you can see we get this message now please enter six some more characters so right now we have a validation for the first password and the second password and for the length and if all these checks go by then you can process the actual passwords that they they've entered and check if they're equal to each other you can technically do all of these checks in one line it'll just be a pretty long line but what that means is you can't have three separate error messages like this if you have it processed in one line the only error message that you can give is very generic there's no one generic message that can fit for password empty and the confirmation password empty and for the length so maybe what you could do is chain the both of them to be check if they're not empty so then you can process a message with something like please enter a password and then you can have another check for the password length just to let them know that they need to enter six or more characters but in these off into two separate checks is going to be very helpful because it'll let the user know something a bit better than a generic error message so in the previous examples throughout the course we've actually talked about using the two lower function and I said in majority of cases where you want actually compare two different things you want to actually use the two lower function or the two upper function and you can achieve this by having two lower just here and then also two lower just here now the problem with comparing if they're both equal to each other but checking the lowercase values is this is indeed a password if you're checking if the user has inputed any capitals lower case symbols Etc then there's no point in applying a too low function because that will just ruin their actual password and reduce the security so in certain cases you don't always want to use two lower and two upper for comparison you want to just check the value straight up and the same thing is when you're doing a login you don't want to be checking their values lowercase because that's their login these are some of the specific situations where you don't want to be using the tow function if the data that you're processing is pretty sensitive and will be messed up if you use the toow function that you should always avoid it passwords fit this perfectly and usernames as well if someone's added some capitals inside the username then you don't want to ruin that by doing lower case or upper case if you're your username is spelled like this and you try and log on like this then they are not equal to each other because this will probably be two different accounts you can have an account with a capital B and have account with a lowercase b so you don't be lower casing the input and then doing a comparison because what you might actually retrieve is a different account than you're looking for so now that we talked about stuff theoretically let's see how we can do things practically so as you heard in the last video arrays are a way that we can store multiple variables of the same data type in one little group so if we had something like Nome 1 = 5 in n 2 = 10 in N 3 = 15 and we had a similar case in one of the exercises like this where we had to work out if a triangle was actually a triangle so we asked user to input three different angles and then we stalled them all and then we added them up after and it looked something like this in total equals num 1 plus num 2 and then finally plus num 3 and then we had some sort of if statement after to check if the total was equal to 180 and then we did something in the curly braces just output that it's valid and then else output it's invalid you can see how this gets a little tedious we have to create a new variable every single time we want some more data to be stored and in this case we just simply want another number that we can store but we have to just keep a pending one to it in that case we could have angle one angle two and angle three but how about if you have something that just called angles for now let's just talk about how arrays work and how we can use them and then after I've went through this example about arrays and taught you what to do with it then I will go get the code from the exercise from the triangle video and actually transform it into using an array so you can see what the difference is and how the new code will look like so let's get rid of this little section so now that we've got three integer variables let's see how we can do this another way so the Syntax for arrays you first type in the data type that you want just like before and then you add on a square bracket and a closed square bracket there's nothing that needs to be inside as of right now then you press space and type in the variable name as per always and then we can make that equal to new in 3 so what this side of the equal sign means is we want a new instance of an integer array and we want to have three positions since we have three variables here that we want to store we need to have three positions to stall them so this line in total says that we want to integer array we want to call it numbers and we want to instantiate our new integer array with three positions instantiate is just the term that we use when you turn something into a new class at this point if we don't use new then we're going to get compiler error because it's unsure what this is trying to tell you it's trying to St an integer inside integer array and that makes no sense so it won't recognize the square brackets in this case because it has no idea what it's trying to do and this syntax is completely incorrect so the compiler doesn't know what error message to give you so we can have a new int and what we can do now is by using the square bracket reference we can actually specify these three variables inside our numbers array so now we have access to numbers 0 = 5 and then if we use controll D to copy this down twice we change this to one and two and then print 10 here and 15 here so now this is exactly the same as this we have three integer variables defined separately as 5 10 15 and now that we've created an array of numbers we can specify all three of these values inside our numbers array so instead of having three individual variables now we just have one that holds everything like a group and just to show you how this works if we have a console right line we can say n one space num two space num three and if we use control D to duplicate that down then what we can have instead of these num ones is simply just place these values inside changes to one and changes to two and what you should notice is these two lines are going to print the exact same values there we go so in this example we've took our sloppy code that will roll us around appending one to this number creating a new array and then printing it out so let's say we want to actually use these to read in values from the console what can we do and you'd use these exactly the same as how you use variables up here this is just an integer variable at a specific position held inside a group so we could simply have a console right line delete the right and just say enter a number and then instead of starting five we can say convert to in32 and then we can have a console. readline and that will read in from the console convert it to an integer 32 and then store it into the first position of our numbers array now if we just copy this down twice and we can get rid of these two lines cuz this is just staring it statically and add one and two to here so now what we're saying is enter a number St into 0o 1 and two and let's see what happens now so now we get asked the numbers 10 20 and 30 and you can see that they've been stored here of course these haven't changed because this is still referencing our static variables up here so what you can see in this example is now that we've made an array we can specify each of the values very easily inside here and if so we wanted to have a number four instead of to duplicate it and rename it and change the value for example we can just simply turn this into four duplicate this little section and then just change it to a three one thing to note in C and many other languages almost every single index will start at zero in the last section we covered the string functions and they also started at zero when you're dealing with strings and their positions when you have a for Loop of the string then you always want to use index zero as the first position the same is true here we have four positions which means it goes from zero all the way till three it never goes from 1 to 4 or from 0 to 4 these are bad values it always goes from 0 to 3 you might be thinking this looks really good but when we go to print it we're going to have to copy and paste this little section add another one and rename this to three this gets a little bit tedious if we just trying to print them all to the screen so let's see how we can fix that we can use a four Loop for this so we can have four in I equals z i is less than and then we can have numbers do length and if you notice from iterating through a string variable the syntax is exactly the same we have a do length property on the arrays as well as we do with a string variable so in order to print out this line what we can do is print one of them every time we go around the for Loop instead of using a console right line we can just use a console right so we can have console. right and then what we can simply do in here is we can say numbers square bracket I and then we can have a space right after it just to M make what happens here we have the number printed out and then a space after it number printed out a space after it and so on and so forth so let's see what happens now if we run the code 10 20 30 40 there you go so you can see that these two lines are exactly same and now what happens is let's just comment these two lines out and if we were to change this to five and we can duplicate the section changes to a four and then now we have five variables started and we don't need to touch this for Loop because the numbers do length will get updated anyway so we can have 1 2 3 4 five and you can see all five variables have been printed automatically what also is quite tedious here is we're having to add another one to this just so we can ask the user how many times that they want to enter a number again this is quite tedious but we also have a fix for that because we know how many times we want to ask the user to enter a number then we can use a for Loop to iterate through and ask the user as you can see every single line here is exactly the same except for the index position that we're dealing with and the same is true for this for Loop this line will always be the same as we're printing out here and the only thing that changes between this section and this section is the fact that this says one and this says zero so we can translate this into a for Loop to make it Dynamic and we can do exactly the same thing above here so let's actually copy and paste this for Loop because we want to do exactly the same approach we want to go through all the positions inside our numbers array and then we can actually ask the user to enter a number in so let's block comment out this massive section and then we can take one of them and place it inside the follow Loop so now we're asking the user enter a number and then we're storing inside index zero and of course if we keep using index zero then it's just going to override the first one and we're not going to store any data so we can change that to an i let's see what happens when we run it now 1 2 3 4 5 and then we get the five numbers being printed this is awesome because what we've got now is five output commands coming straight to the console just from a for Loop the for Loop is responsible for printing them all out to the screen reading in the value convert it to an integer and then store it inside our array and then we have a separate for Loop to print it out to the screen what's really really powerful about these two for Loops that we've built is if we want to have 10 numbers now we simply just change this to 10 and then just rerun the code as you can see we now have 10 numbers there you go so what we've just done if we move this code down a lot now just so we can have it close by we've made our entire program that was actually pretty lengthy in into just a couple of lines and two for Loops one for Loop is responsible for looping x amount of times x depends on whatever that number is and then we go through and ask the user to enter a number read in from the console convert it to an integer 32 and start within the array after this for Loop has finished running then we have all the numbers stored inside our array and then we can go through and print them all out to the console another way we can print this out to the screen is by actually using a for each so we can say int num and then we want to be a number inside our numbers so for each of the integers inside the number we want to create a new local variable called num and then we can use it in here and if we take this line and copy it down everything's exactly the same except we don't need to specify the main array numbers now and we don't need to specify the square brackets we can just change this completely and replace it with n and if we just make this number smaller so we don't have to Output a lot of values 1 two and three and you can see that they're exactly the same there's no line between them because I don't have a console right line so let's quickly add that in and there we go 1 2 3 and you can see they're outputting the exact same values the reason why I needed a console right line is because these four Loops are using console. right the problem with console. right is even after finishing writing all of the lines it doesn't continue to the next line it stays there so if I don't break up the two outputs with the console right line then all six outputs from the console right and the other console right will all go on one line this is just for demonstration purpose anyway either one of these Solutions are fine more people tend to use this one the problem with these two options is you can't always use them interchangeably this one will always go through every single position it will always go from zero and it will always go to the length the problem with this for Loop is you can't choose how many times you want to iterate through before you stop there might be a very specific case where you have a big array of data but you only want to select the specific range if an example where you had a th000 array positions so from 0 to 999 and let's say you wanted to request and run a for loop from 500 to 600 so you would literally type in 500 in here and then 600 inside here and this would be fine as long as your array has that many positions but with the four each Loop Loop if you run for each loop on a thousand length array then it's going to go through every single position in some cases you might not want that and you only want to go through specific cases so if you know you're going to go through every single case then you can use the for each but if you know you're going to go through a certain amount of cases then it's always best to use the fall Loop okay so we covered quite a lot in this video so let's just have a recap so initially we started off saying we have our num one num two and num three then we had our static variables St inside there and then we created our integer array which is now down here and just to make it a little bit easier to store multiple variables because if you wanted five variables you'd now have to duplicate that and change that to number five and this will get very tedious if we had something like 10 like before this is very long and you don't need be specifying number 10 in your code because this also hurts the readability of it using arrays can solve this problem quite a lot you can easily specify array using this notation int square brackets followed by the name and you make that equal to a new int three the three can be any number that you want as long as it's a whole number cuz this tells us how many positions that we've got we then outputed lots of values to the console and read them into our Ray but we had the same problem as we did above where we just had to keep duplicating the sections so what we did to prevent that is by writing a little for Loop that went through every single position in numbers array I puted something to the screen readed in the value converted it and stored it into the array and then after all that was done we can use a for Loop or a for each Loop and print that back to the screen now that we finished the base cont of this video and because I said at the start that I was going to take the triangle exercise and convert that into an array so let's do that now so now I've copy and paste a solution from the triangle exercise straight into this project I've just block commented everything above just so it doesn't interfere with our code so let's just run this code to familiarize us with what's going on so if we enter 60 60 and 60 then it says valid and if You' run it again and enter something else that doesn't equal to 180 then we get invalid so let's see how we can make this code a lot better by the use of arrays so as we said before we don't want to be using this angle one angle two and angle three let's make a int square bracket angles equal new int and then in this case we have three angles and what you could do as well is you could say con int angle count equals 3 and then you can simply use that inside here so later on in the code if we wanted to specify this to a different value we can just change that later on so now that we've got the three angles we can get rid of these three lines and write ourselves a little for Loop so I goes from zero all the way to angles. length and then every single time we go around in the for Loop we want to say console right enter angle one and then we can say angles square bracket and not zero in this case cuz we don't to be specifying index as it will go from 0o to 1 to two we want to be using I I because we're inside a for Loop that's already going through all the indexes forers and make that equal to convert to in32 and then a console. readline now we've got all the values stored inside here let's do deal with this problem so if we just comment out the total for the time being let's run the code oh we have one more error down here sorry let's run the code again and we can say enter angle one and we can type the values in but as you can see we've got angle one for each of the times what we can do in here is use our I index to print out the value so we can turn this into interpolation and then wrap the one inside curly braces and we can simply change this one to an i and let's see what happens now so we have enter angle zero and then one and then two and this is fine but humans don't like reading zero they like reading 1 two and three so what we can simply do is say I + one and because we're using I and then adding one to it it's not going to affect the variable inside the for Loop so there's no problems by doing this this is simply just for the output purposes so now we can have 1 2 and three just show up like that perfect so what we can do now that we have all the angles stored now we need to replace this line by writing a for Loop that can add up all the values for us so we can have for each in angle inside our angles and we can just say int angle sum plus equals angle the problem with this is we can't specify a new variable inside here and then use it outside an if statement so what do we do in this case you want to take angle sum and initialize it outside the for Loop and then give it a value of zero and then inside the follow we can remove the int and we can say angle sum plus equals the whatever angle that we're currently up to so if we had three values that's going to say 0 + 60 and then take that value and add another 60 and then take that value and add another 60 so it'll keep a running total for us and if we just print out angle Su to the screen let's see see what happens 10 20 30 and now we have 60 and that's the correct calculation if you add them three together so now that we have a running total for angle sum then we're pretty much done if we get rid of this line of code which is our previous total and we actually bring back our if statement there you go there's no error now and all this is doing is checking if the angle sum is equal to 180 and then print valid and invalid so we can have 60 60 60 and it prints out valid and let's just comment out our output and then we can have 60 60 59 and then it prints out inv volid which is exact same behavior that we saw at the start so let's remove the extra code in here and keep it like this there you go so now we've got our solution just like this and it's a lot better because if triangles were to transform in the future and we wanted more than three sides then we can easily update this value because now that we're using arrays or we're using a for Loop to enter out the values what we can do we don't actually need to store it what I mean by that is we can actually just get rid of this array completely let me demonstrate we can take this angle sum and place it underneath here we can keep the count so we can use that in the for Loop so we going from 0 to three because that's our angle count and then we can get rid of all this and let's see what we can do now so we have an angle count equals 3 so we go from 0 to three which will'll just do as we said before from 0 to two because it's less than the angle count and let's just print this to the screen see what happens so the output still exactly the same but what's happening is these values are not being stored they're just being shown to the screen and then not done anything there is no equal sign here to assign it into anything so what we can do is we can say angle sum plus equals the value straight away and now if we try it 60 60 60 then we get valid the main differences between the these two situations is in the first one we used an array to store all the different values and then we added the total but if we're not going to use these values after then what's the point in storing them we can just use a for Loop to ask the user how many times they want to input the values and then just add them every single time that they add the calculation in and at the end we could just simply use a conditional operator to be able to print at the screen whether it's valid or not but let me just undo that solution so I can show you the array solution and we can have a quick recap that was just an extra little tip just in case you wanted to know what different ways you could use to make this work there we go so let's just have a quick recap here so we have a Conant which all we'll do is let us specify three inside here and then we can use it here this isn't entirely necessary but it does clean up your code a little bit because it gives this number three a bit of a meaning it says the amount of angles is our angle count having a three left over like this is what we call a magic number they're quite bad because it hurts the readability of your code people want to know what the three actually means so if you bring in an angle count then you can actually read we want a set of angles and this is the amount that we need and that's denoted by angle count it adds text to a variable it gives you a way of making sure that the text equivalent of a variable is present so someone can just read it after we've created our integer we can actually make a for Loop that goes from zero to the length and then we ask the US it to enter the angle and in the previous example we had enter angle one 2 and three so now we can mimic that by using I but because I starts at zero we want to use plus one every time we loop around the for Loop we ask the user to enter the number read it in through console read line convert using convert 2 and 32 and then store into the array after this for Loop is finished we have all three values stored in the angles array and then we have an In Sum to count up all the values that we need and and then we use the fall Loop to go through every single integer value inside and make a running total and store it inside angle sum once angle sum has the total count then what we can do is use console right line along with the conditional operator to print whether it's valid or invalid to the screen in this video we're going to look at how we can use the built-in array functions to be able to sort an array so if you have an INT array called numbers and then using the previous notation that we looked at we can actually specify any numbers that we want using a common delimited list so if we just have nine numbers inside here then we've actually defined an integer array and then the compiler can count the amount of items that are inside here and give it the length but we don't have to worry about that ourselves so if we use a for each and we can just print Inn inside numbers we can do a console right line on the new local variable called num if print it out we can see all of the values and maybe we can actually just use a console right followed by a space just to give them all on the same line there we go so as you saw before if you had a string called test and we wanted to do something to it for example if you wanted to use the replace function if you want to remove all spaces with an empty string then if we check the replace tool tip we can see that it returns a new string most of the string functions will return you back the new string after doing something with it but in this case if we type type in Array followed by do sort and we can place our array straight in the bracket what you'll realize is if you hover over sort it will sort the elements in the entire array but it will indeed return back a void and void just means it returns back nothing so in this case what it's doing is you're actually affecting the numbers array straight away and you don't have to do numbers equals array. sort numbers for example if we were doing the test replace we would have to do this otherwise this would just be returning back a string but we wouldn't be using it the same is not true for the arrays when you run the array functions they tend to return back void and you don't have to do anything other than give it the array that you wanted to sort so now if you run this code you should just see the same output since they already sorted anywhere so let's change some of these numbers up and just see what happens now there we go 0255 6 7 899 and that's it sorted just like that there isn't a whole lot to this sorting function but what you should note is you can use this new array syntax to Define how many items that you want in there instead of having to change the amount of positions that you have using the square brackets you can just denote any number of items that you want inside the compiler will count them for you and press the length straight into the brackets for you so you don't have to worry about it using the array. sort function all you have to do is give it the parameter of the array that you want to sort and it will affect the array straight away and you don't have to restore it and then we're just using a simple for each Loop to print them out to the screen in this video I want to discuss the array reverse function so if you hide an INT numbers equal new int and if you just had lots of numbers in here defined just up to five then we can add a semicolon and again using this array function we can see array. reverse and pass our array inside and then we can just use a for H our item inside our numbers and simply just print them out using a console. write and we can use string interpolation I just put a space at the end there we go and if you run the code then you can see our numbers have just been reversed there isn't a lot to this video I just wanted to show you about the different functions that you have available for arrays these can come in handy when you have something like a list return from a database for example and it's ordered in a certain way let's say you're returning back a list of lots of people who ordered back alphabetically and it's going from a to zed and let's say you have some sort of user interface that allows you to flip the order instead of having to request the database to get the data back in the opposite order you can use this array function to just reverse the list the same thing goes if you're trying to order by lowest price or highest price you can use this to show the different values in different orders that's where this array function comes in handy when you have different situations like the names or the price by ascending or descending where you can just flip the data and instead of having to request it back from the database again flipping it locally is a lot easier than going back to the database as that uses more data and more computational power on the back end and then return it to the front end it's always best to be able to use these functions instead of having to use external things to be able to return back the same data using it locally like this will give us a performance Advantage because it's done directly on the data instead of having to request everything again if you wanted to do this manually let's have a look and see what your options are you can have your integer array just defined like this with a dynamic list and then we can have a sorted array using the same length as the current array what you can do instead of using reverse we can actually just comment these lines out you can bring back a normal for Loop but if we use two RS it gives us a reverse Vol so the length is going to be our numbers do length and the rest of the paramet is exactly the same we want to go from the last minus one all the way till zero and we want to decrement in one and we can say our sorted number I is equal to numbers I but all this will do right now is just give us back the same value stored so what we need to do in a case like this is make another variable something like X and we can store that into zero and what we can say is X is assigned the value of whatever this numbers is because this is going backwards but we want this one to go forwards CU we want it to be reversed and we can say x++ and see what happens when we run it now so so nothing's going to come up because we don't have any output so let's use a for each we can have V number inside our sorted numbers and we can just take this and place it in here and just print out the item and we can use num and there you go it's been flipped the exact same value is just the other way so this is obviously a little bit more complicated because you have to use an additional variable use a backwards for Loop and then incom your own separate variable and as well as completely make a whole new array of course you should only do this if you need it as two separate arrays if not you can always just affect the one that you're up to right now because I said before that arrays are actually static data and they're going to be fixed size then there's no way to remove or add an item but you can clear what you have already so let's have a look array do clear set a range of elements in an array to the default value of each element type so the first parameter takes our array so let's use numbers and we want to start off at the index that we want to clear from and let's just say zero and because we want to clear the entire array let's go all the way to numbers. length and now let's just produce a for each of our item inside numbers and then just have a console right string interpolation which just prints out the item followed by space and now let's run the code and see what happens so we have lots of zeros in the console and this is to be expected because as we've talked about before for the default value for an integer is indeed zero so all this is doing when it says it's clearing it's just actually assigning all of the positions the value of zero and we can mimic this quite easily through a for Loop so if we comment this out and write ourselves a for Loop in I equals z and we want to go to numbers. length and then simply inside we just want to say numbers square braet I equals to Z what you can also write is the word default this will pick up the default value for the data type that you specified you can type in zero or you can type in default it's up to you but I think in this case if you're trying to reset it back to default then you don't have to worry about remembering it or any typos you can just use the keyword default so if we run this code now let's see what happens so effectively we've mimicked what this function is doing but let's have a look and see what other parameters we have access to so if we comment this out and drop the value then you can still see we only have one Constructor normally you'd see the open down arrows on the left hand side to say one of two in this case we only have access to one Constructor it will only give us a range of elements we want to remove but really we just want to clear it does say here in the tool tip the array whose elements need to be cleared and because it is a clear and not a remove you got to remember when using this function it doesn't actually remove any of the positions it just resets the values inside the array so what we can do in this case is we can say numbers comma 5 comma 5 and what that will do is the first parameter is where you want to start so if you want to start at the fifth position and then we want to count five forward and because we have 10 numbers then this should return back okay let's comment out this for Loops it doesn't take an effect and let's run the code and see what happens now so now we took the position five which is actually the sixth number because it's zero base and said we want to remove five forward so itself and then P more forward and there we go we have five numbers being removed so instead of removing all of the different values we can actually clear a certain amount that we want and to mimic this in a for Loop we can do the following we can start it at five and we want to go to 10 and let's run the code and you can see the output is exactly the same when doing in a for Loop you need to actually calculate what this is going to be so we need to take both the numbers the fifth index and the five length which is 5 + 5 and then we get 10 and we don't make this less than or equal to 10 because we have 10 numbers so actually want to go from position five to position 9 which will equate to less than 10 we actually want to go from position five all the way to position 9 which actually covers five numbers 5 6 7 8 9 even though it feels like the difference between the two numbers is only four because 9 - 5 is four but we actually have five numbers between that 1 2 3 4 5 there we go so when we print the values from 5 to less than 10 we're going from 5 to 9 which is exactly what this is doing this is the index that you start at and this is how many numbers you want to count forward so let's just have a quick recap of this function we defined our numbers array using array. clear it doesn't actually clear the values it just gives us access to removing them back to their default values it doesn't actually clear the array it just resets the the values back to their default type we can have numbers parameter which will equal to our array and we want to say we want to go from index0 all the way to numbers. length which will be every single value inside the array and all that will do is go through the array and set them all to their default value which is similar to what this for Loop is doing and before we had inti equals z and I is less than numbers. length and that will go through every single position you can technically use zero instead of default but that would mean you have to remember the default value of every single data type it's easier to just write the default keyword and it doesn't promote any typos using the default keyword is by far the easiest and the most safest option if you're going to have this situation so making every numbers index equal to default in this case because we're using integers it's going to assign the value of zero and then after this voles run with I is zero and I is less than numbers. length it's going to make all of these positions equal to zero which is in essence what this function is here for because arrays can't be added or change in terms of the values that they have after they've been created you can only really modify what's already there or you can reset them all back to zero using this notation from zero to numbers length you can get rid of all the values and make them all zero using five to five means it'll start index 5 which is the sixth position and then go five numbers forward so it will delete these and reset them back to zero you can mimic is and a follow Loop just like this start in I at five and then go to less than 10 and the reason why it's less than 10 is 5 + 5 gives you the 10th index but because it's I is less than 10 you actually want to go to the ninth index because from 5 to 9 that's actually covering five different numbers and then we can go through and assign the default value and then when we print it out you'll see that all of these numbers have turned into zeros just like so searching through arrays are very helpful when you try to find some data inside your array and you want to return back the position to maybe do something else with it so let's have a look at this example so we have a numbers array and let's say we want to search number 199 and find the index of it so first let's ask the user what the number they want to search enter number to search then we can have in search is equal to convert to in32 and we're converting the console. readline and then let's have a look at the function so inside the array Library we have an index of searches for the specified object and Returns the index of the first occurrence in a one-dimensional array this is very important as it says the first occurrence which means if there was another 199 at the end it's only going to return you back this one and then stop immediately and not give you the value of this one so let's have a look in the parameters and see what it takes it takes our array and then a value so our array is called numbers and the value you want to search by is our variable called search if you hover over the index function again it says that it returns back an integer zerob based index of the first occurrence of the value in the entire Ray if it was found otherwise the value is going to be minus one so we can say in position is equal to this and because it says if it's going to be found then it's going to have the value of a zero index and if it's not going to be found it's going to have the value of minus1 so we can say if the position is greater than minus1 because if it's greater than minus1 that means the value is zero onwards we can also write this by saying if the position is greater than or equal to zero it's just up to you they both mean the same thing and then we can say in here number search has been found at position position there we go so let's run the code and let's do a perfect situation so we can can say 50 and you can see it says number 50 has been found at position three and that's the fourth index since it's zero based and what you could do if you wanted to is actually add one to this just so it looks like a bit more of a readable number because four is going to be the fourth number 1 2 3 4 and let's try find a number that hasn't came up like 60 it's going to return us back with nothing this is really bad because it looks like the search has failed which it has but you need to Output message to let the user know so have conso right line and say number search has not been found let's type that again 60 number 60 has not been found so let's see what we can do to be able to write this function ourselves if we just block comment this for the time being we can actually use in position equals to minus1 and the reason why I make it equal to minus1 because when we read the tool tipe of this index function it said if it's not not going to be found it's set to minus1 so why don't we set it to minus1 first and then we can try and find it so in I equals 0 and we want to go to numbers. length and inside here we want to scan each of the positions so we can say numbers square braet I and if that is equal to our search then we can set the position equal to I if the number we're up to is equal to what the user has typed in then we want to set our position to the index we're currently up to and we don't need to have an else because we've already set it to minus one and after the for Loop we can actually take this if statement and put it back down here because the code's going to be the same if the position is greater than minus one which in this case is our default value so in essence if this value has changed then this should always pass EG we've found the number so let's run the code and let's type a number in 30 now it's found at position five now if we try 60 again number 60 has is not being found there we go so this function is exactly doing something similar to this it's going through every single position finding the variable and if they match assigning the index and then after just returning back to position back to the console so let's comment our example and let's see what other variants of the function we can use and let's comment back the first one so using this line we can duplicate it and just comment it so we have some other parameters inside here if we add a comma we can actually give it a start Index this is the starting index of the search and let's say you only want to search from the second number onwards then you can just type in the number two so now if you've run the code and type in 90 it's going to say 90 is not found cuz 90 is the first one and let's try a value like 50 now it says the number 50 is being found at position four because now it's included in the range from two onwards because this is two onwards it'll be position two until the the end of the array if you wanted a very specific range then you can actually give it another value so we can say we want to go from zero and then we only want to go to forward so if you run that now and type in 22 it says it's not being found cuz we' started here and we said 1 2 so now it's only searching between 90 and 199 and if you wanted to include the middle ones you could say you want to start a position one and go to forward so now you get these two numbers and so on and so forth so now if we try number 90 you'll see it's not being found because 90 is not one of these two the reason why you'd use different ones like this if I revert back the first one this will go from two till the end this will go specific range and this will go through everything the reason why these exist is if you have a very very big array let's say it's a th000 indexes then you don't want to search everything unless you really need to let's say for example you had a names array and it was sorted off alphabetically and the person's name that you wanted to search began with an a there is no point in running the search all the way from a to zed if you know it begins with a and let's say for example you found the first index of the user that has a name B so you have now the indexes from the start of the array up until the last array position that has the value of someone's name beginning with a so now you have the two indexes of every single a name inside this array if this was a this was B and this was C and this was D and you had these two positions then you should only be searching all of the a names instead of searching the entire array and the reason for that is you'll be searching lots more data for no apparent reason and it's going to take an extra long time for searching something that you're never going to find if you're searching for a name that begins with a there is no point in searching for anything a BCD and so on and so forth that's where you'd use the very specific range you can say you want to go from zero all the way up to the first B name so then you're only searching the a names this is just one example and there is a lot more every situation is very unique so use the parameters that you want and always use the ones that can get you the best performance the least amount of things that you can search is the best way forward if you don't know what you're going to be searching then you should always use the top one which will just search everything if you know where the value is going to be or roughly going to be the then you can use this one or this one to give you a better range and it's a bit more focused instead of searching for everything so a quick recap of this index function what it will do is it will return you back to position if it's found it the position will be zero based just as arrays are if it hasn't found the position then it's going to return this variable with minus one so therefore after you've run the code you can check if the value is greater than minus one which will be from zero onwards if the value position is z onwards then you know that that number has been found and you can use the position variable to Output that to the screen if the value position is minus one it means the array index function has returned back negative and the value position is now minus one so you can output to the user that it has not been found just in my little explanation down below you can see that we can mimic this function by setting the value of position to minus one using a for Loop that goes from zero to numbers length and if you wanted to as well you could use these inside here if you wanted to mimic this this goes from two till the end so you can say I equal 2 and you still want to go to the length this one goes from one and then to ahead so you can actually put I equal 1 and then because it's two ahead from one instead of numbers. length it will just be I is less than three because 1 + 2 gives you the three so in order to do this manually you can Lube through the elements that you want check if the number you're up to to based off the index position of I is equal to the search variable that the user typed in up here and if you find a match then you can assign the position to the value of I after the for Loop is run you can check the same if statement as we discussed above these are copy and past it down below just to give you an example in this little section all these arrays have static data which means that when you initialize them with a certain length you can't increase that length or decrease the length you can only modify the data inside it and you can't delete any rows if you create an array of size five and you only store three people in then now you have two positions that are being unused and that's unnecessary amount of data stored in your memory if you're not going to be using it up in certain situations like when you're making a game for example Tic Tac Toe then you know you're always going to need a 3X3 grid so a 2d array will be perfect in this situation cuz you know the exact width and height height of your array so you can do this perfectly whereas lists are quite Dynamic if you don't know how many people are going to be within a system for example if you're signing up some sort of register for a class or for a school or something of the sort and you don't know how many people are going to be in that class then you can use something called a list a list a dynamic cuz what you do when you initialize it you just say that you simply want a list and you can add items and you can remove items and you can also modify them if you wanted to expand the size of an array it's slightly complicated but it's not impossible so if you had int numbers equals new int and let's make that length four and let's say we had a numbers array that we wanted to increase to length five we could have new numbers change that position five and then what we're going to have to do is from position zero all the way to three which is our fourth length from the numbers array we're going to have to copy that into 0 to 3 of the new numbers array so now they have the extra data plus the last one which will give us our four so that'll be five length 0 to three gives us our four numbers and then we have one empty one so we've just made a new array and then copied all the data from numbers into new numbers now of course this is not really practical that if you want to reduce the size or increase the size you're going to have to do this each time of course you don't want to do this you just want to use something called a list so let's stick with an example and see what we can do so you make this and three and let's just put three numbers inside here if you remember from the array video we can also declare it like this we can say number 0 equal 1 and then one and then two and change these values these two are doing exactly the same thing I'm initializing it with 1 2 and 3 and also just saying that all the positions in here are equal to 1 2 and 3 so we don't need this twice but I was just showing you as a quick recap so we're declaring array we're calling it numbers and we're giving it a length of three and initializing it to 1 2 and 3 now let's see the syntax to define a list you start off with the word list and then you have a left and a right arrow which makes a little section inside the section you actually want to State the data type that you want so if we're copying the numbers array we can have an INT inside here and that's it for the Declaration of the data type and then we can say new numbers or List numbers equals to new and then there you go it gets Auto filled for you but let's just type it in we have list open the arrow in in the middle and then close it so now it's the same on both sides but because this is a new we need to add a Constructor so we can open the curly braces and the first Constructor says initialize a new instance of the list class that is empty and has the default initial capacity press the down arrow we can give it a capacity of the number of elements that the new list can initially store so we can start it off with five length or three length or whatever it doesn't actually matter it just means that we actually have three positions available immediately if we place three in the brackets and the last one we can actually give it entire collection so let's say if we loaded a list of numbers from a database or a list of something from database and we can actually insert it straight into this list by putting a list inside these brackets of course right now we don't have a list that we're going to assign it with so let's just leave this empty and close the brackets and add a semicolon so we could say list numbers do add and then we can add one and then duplicate this down and add two and add three so now these two have exactly the same contents instead of doing this you can have the same notation like this so you can have the codyy braces in here and we can put in one 2 and three now that's doing exactly the same thing and you see I can just keep adding more numbers in here and the list simply doesn't care but as soon as I add one more into here then I'm going to get a syntax error because it complains that the length is not equal to to the numbers that we have because the list are really Dynamic it doesn't matter how many you put in here because it can just go on forever of course until you run out of memory so let's have a little working example just to see how this works so we can have a for Loop and we can go from 0 to 10 or maybe 0 to 3 just so we don't have to enter as many values we can have a console right that kind of just says enter a number and then let's read that in and we can say in n equals convert to in 32 and we can place a console. readline inside here and then after we've got the console read line we've got an inome that's being converted from the console input inside our integer num and from there we can take our list numbers do add and we can add the num inside there or if you want to reduce a variable you can just take this line and place it straight into here now if you get rid of that when this fall Loop runs will have three iterations let's run the code and find out 1 2 3 so now we've ented three numbers and now they've been stored in the list so let's create a follow loop after and we can go from zero all the way to list numbers do length but of course when we're using list we don't have a length anymore when we're using arrays we have length because arrays have a fixed length whereas lists have a count of the items inside it so instead of length we simply use count and then inside here we could just do what we normally do and say list number numbers square braet I and let's run that and we should see the numbers printed back out in the exact same order 1 2 and 3 and the same principle goes if you use a for each Loop we can say V item inside list numbers and that's all you need to do and you can just print item to the screen now we should see the same output twice let's have a look at other values that we have inside here so we type in list numbers Dot and let's have a look at the functions inside so we can add which you just used above we can convert it to an array we can remove a specific position and we can clear it completely they have other ones in here like binary searches we can check if it contains a certain element this is going to be very handy when we do our remove we can convert them all to a different type we have a copy to we check if a value exists inside we have a find finding all of them the difference between these two is the find will return back the first one whereas find all will retrieve all the elements that match it finding the index of a specific match finding the last index iterating through them all you can insert a specific position whereas the ad will just insert at the end of the list adds an object to the end of the list inserts an element to the list at a specified index and then you have remove which gives you the first occurrence so you can type the number straight into there so you can ask the user what number do you want to delete and if they type zero it will delete the first zero in the list and you can can remove all so if you want to remove every single zero inside the list you can do that as well or you can remove a specific position this is the most used function because what you can do and what you can do is use the find index search for an element that matches a condition and then returns zerob based index the first occurrence so if you want to delete the number zero from the list you could use find index and that returns you back with an INT and then you can use the remove at and then pass that index straight into there you can also sort it so it goes up in number order we did this with the array. sort function as well and if you wanted to you can also reverse the entire list this can be very helpful as we did with the array functions if you just wanted to reverse them all in case someone had something like a filter when you're doing from Price high to low and low to high the difference between them two lists is simply the list flipped so let's run a remove just inside here and let's see what happens so we can say remove that and let's say position zero so we type in 1 2 and three you'll see that 1 2 3 gets printed out and then I'll hit this remove at and it will delete the first index and in this case the first index is going to be our number one so now this has became our first index and this is our second index and it's got rid of the number one so let's move on to a different data structure called dictionaries dictionaries are generic collections that store key value pairs in no particular order they take in a t key key and a t value and these just mean the key and the value can be any data type that you want dictionaries come under the system. collections. generic namespace and if you don't include this line at the top then you'll have to type in system. collections. generic space dictionary every single time you want a specify dictionary putting the name space at the top will include it within the project and you can use dictionaries freely so one thing to know is the keys must be unique and they cannot either be null values can be null or duplicate cuz they're the value values depending on the key as long as the keys aren't the same then the values can be similar so let's have a look and see what we can do we can type in dictionary and you can see it has the arrows either side and you can see here it says T key and T value and what T key and T value is is it gives us the flexibility to add any data types that we want we can add in two strings in here for example or we can do anything that we please so in this example I just want to start a list of names and I want to give them a unique identifier and this unique identifier will just give them a number that their profile is up against it's the same way whenever you make an account with any sort of website when your data gets stored in the database you have a unique ID for your account and this is the same thing that I'm trying to replicate here we have a unique ID and with that unique ID comes a name so we can say equals new dictionary just like we do with the list we can end the brackets and end the semicolon there and now we've created our dictionary and the exact same principle we can use with the list we can simply type in the name of the variable of the dictionary and type in add and then we have access to int key and string value and this parameter is going to change if this now becomes a string as I'll show you now and if we reopen the bracket you'll see this has turned into a string key so that will change depending on the data types that you specified so let's say we want to add one and we want to add ourselves then we can dup at this down and add in two and three and we can say test and test and now if you run the code you'll see that we have no errors and nothing's going to show up I'm just demonstrate that it compiles okay and the same thing with the list we can also simplifies the initialization process and it looks something like this so because this is a key value pair we can no longer just type it in one line they need to be in a little block so when we wrap these around the curly brace we can have the key on the left left and the value on the right and one of these is called a key value pair key value pair and we will use these in the for each Loop in a second when we print out all the values to the console so let me just demonstrate something about what I said at the start I said that all keys must be unique and there's a reason why I said that if we duplicate the first entry therefore giving us the same key as one and we try run it and let's see what happens we get something called a runtime error this runtime error happens when we run the program and it's got nothing to do with compile time or our logic an item with the same key has already been added so we need to watch out if we do this because our program is going to compile but it's not going to work at runtime and let me demonstrate another fact if we make this number four and our values are exactly the same once we run this it will still work fine values can be the same but the keys cannot be the same the keys have to be unique so just like with our lists and our arrays we can use a for each or for Loop to access this directly so we can say 4 in I equal 0 and we want to go names. count and the same reason it to do count for a dictionary as it is for a list but it's not for an array dictionaries don't have fixed length and neither do lists they are very Dynamic and basically are a list list can only store one different data type whereas dictionaries give you a key and a value so as we said above we have a key value pair so let's try and print this and see what happens have a console right line we can say names square bracket I and that will give us back the position the issue with this is it will just give us back the string and let's just see what happens if we print this then we get an exception because no key was given and the problem with this situation is we can't use this like a list Geto sets the value associated with a specified key what this means is when we give our square bracket I inside here this is actually not talking about the index this is actually trying to do a search on these keys so if you actually change this to one then we should get ABA return back this is not actually doing an index Lo up it's doing a key lookup and the reason for that is what we're going to have to do instead is say names do element at and then what we can do inside there is place our index so this element art will return us back with the key value pair as I said above here so how this variable works is we can do key value pair and then we need to specify this variable the same way we've got it up here so we have an INT inside a string and then we can say a pair and make that equal to the function called element at as that returns us back with a key value pair in string and of course if you wanted to make this a lot smaller you could just simply use VAR but let's keep it as key value pair just so you can understand what's going on and the reason why we need to get the key value pair is if we want to retrieve the integer and we want to retrieve the string and now we can use pair. key and pair. value and because these are both integer and this one is a string it matches our pair exactly so we can take these values and go to our console right line and we can say something like this use string nipulation and say pair. key and then maybe add a hyphen and then say pair do value and then just remove these two lines and let's try and run it now there we go so we get all the values and it doesn't matter what this key is it can be something random it doesn't really make a difference like I said this doesn't have to be in a specific order so let's keep it as 1 2 3 there we go so you can see using a for each Loop to print this is a little bit more complicated let's have a look and see what it takes when you use a for each Loop for each VAR item inside our names and as you can see here our item is automatically a key value pair of int and string and again what you can do is type this straight into here just so you can get used to the notation and there you go it's still a key value pair and then now what we can do is we can take this exact line and paste into here and instead of pair we have item and this should return us back the exact same values and if we just separate with a console right line there we go okay so now that we've understood this let's take a look at an example let's comment this out and let's create another dictionary so we can say dictionary and then we can have a string of string and we can call this teachers equals new dictionary string of string again and we can add our curly brace just so we can add our Valu straight to here so as you said before we need to open curly brace and close curly brace and then we can say the math teacher is called abber and then we can add another one and we say the science teacher is called test there we go so we've initialized our teachers and we said that the value that we want to give it is a unique identifier which is going to be our string assigned to the subject and this is going to be the teacher that is assigned to this subject so what we can do inside here is we can have a console right line and we can do something like this so remember when I was saying in the for Loop we can't actually use the square bracket notation like this because this is inferring to a key rather than a position so we had to use element at just to find out the key value pair and then to print out to the console so because the square brackets is an actual sech let's try and make use of that now so we know that there's a math class available so we can type math in here and what does should return us back is abber there we go so what that's doing is it's searching through our dictionary find ing this element inside here and then return us back with the value for that key get all sets the value associated with the specified key the problem with using this approach is it says here if the specified key is not found a operation throws a key not found exception let's just say for instance I mistyped the math and now we're just going to get a runtime error and it's going to be a horrible exception and our code is obviously going to break this is similar to what we do when we have int. trass we don't just trass it immediately and convert it it without actually checking if it's a valid value so instead of doing this line what we can do is we can check if that key exists first before we then use it so we can say if teachers do try and get the value which is a similar to what we have with trass and then the first parameter is the key that we want which is going to be our math and then out here is going to be the variable that we want to Output out so we can say out teacher and then open the curly braces and then inside here we can print out the teacher so we try to get the value for Math and if we found that key inside these then we return back the value inside our teacher the same way works for our tripassure if it successfully passed it and if it hasn't we can say cons output math teacher not found so let's try and run that now you see we get return back abber and if if you actually drop the lower case then it says the math teacher is not found alternatively what we can do inside here let's assume that this is correct we can take this value and place it straight inside the square brackets and do this again this is kind of redundant because we've told it to get the value for key place inside teacher and then we're just going back to the dictionary to get the value twice so make sure if you have an output variable that you actually use it inside here you can see that you're not using it when it goes a slightly dark color like this so just like in the last examples when we were placing values inside our list we can also do that in dictionaries we can say teachers square bracket math and then we can make that equal to something so if the math teacher were to change and now the teacher's called Joel then we can run this line and print out to the screen let's just take that for each Loop and tailor it to the new dictionary and see what happens when we run it so let's just change this into our V to make it simple and then we can have teachers inside here there we go so now let's just run this and see it now it says abber is the first value the abber is coming from console right line here that says teacher this is one line before we change it and we change the value of the math teacher to jaw on the next line and there we go it's committed the change and just like in the last video as well when we try to delete something from the list let's see what we can do to delete it from here so we can have teachers do remove and you can see that it says key in there and again if we add the key in like this then it's going to work just fine there go we just have science we don't have math anymore but if I drop the lowercase then it's going to cause us back with an error but in this case instead of it thrown an exception like it did when we were trying to do up here and up here as well the problem with using the remove is you just simply won't remove it but what it will do is it'll give you back a building if you remember from the last video we actually had a look at a section where in the list it gave you back a booing whether the remove function worked or not alternatively what you could do instead of using the remove function is to check if the item exists in the first place we can say contains key and we can place math inside here and if it does contain it then we can run the same line of code and we can say remove and then use math just to make sure that this is has been actually removed and then in the else we can say math not found retrieving values back should be retrieved using try get just so you don't cause an exception if this is not found we can simply do an update by placing the value of the key inside this square brackets and then simply just assigning it to something else this assignment will change the value of the key which is inside the teacher dictionary and if you wanted to remove something it's best to use the contains key just to check if it contains it first and then you can do the remove and then if it doesn't contain it you can tell the user that math has not been found and then finally we can just print it out like this so in this exercise I want you to create two lists with the integer data type one for even and one for odd and then we're going to Loop through from zero all the way till 20 and if the number is even add it to the even and if the number is odd add it to the odd list and at the end print out all the values for even and for odd I know you can just print these out inside the for Loop we don't have to have dedicated lists but this is just for list practice and I want to talk about different ways that we can do this solution so let's start we can have a list of int and we can say odd new list int and we don't know the size so we're just going to leave the gap empty and if we duplicate this down we can simply just change this to even now the reason why we're doing lists we're going from 0 to 20 of course this 20 value could be anything it could be a million it could be 100 but we don't know and the point is lists have counts whereas arrays have length if we set the array length to something like a thousand we know probably be able to contain all the numbers inside there but that's going to be a lot of positions that we don't exactly need because arrays are not really dynamic because they're static then it's it's best to use list in this case because we don't know how many numbers are going to be odd or are going to be even between this range if we knew the exact number of positions that we needed in a given solution then array would be better since you don't want it to be dynamic if it doesn't need to be so let's start you can have a for Loop that goes from 0o to 20 if you want to include the 20 as well we can just place an equals the best way to determine if a number is odd or even is to use the modulus operator so we can say I percentage 2al equal 0 and what this will do is it'll tell us if I is divisible by two if the value is equal to zero if you have two modulus 2 then the remainder is going to be zero if you have three modulus 2 it's going to be 1 * by 2 which gets you to two and then to go from two to three you actually have one so if you insert an odd number and do a modulus 2 you're going to get a one returned if you do an odd number and you do modulus 2 then you're going to get one returned if you do an even number modulus 2 then you're going to get zero returned so what we can do in here is we can say even do add and then we can simply add I and then in the else we can also simply just do odd do add and then have I because the values of the remainder can only be Zer or one we don't need to have an lse if in here doing this is a little bit redundant although it's still technically correct the values can only either be zero or one so if you run this calculation and the value is zero if you run this calculation and the value zero the only other value can possibly be is one so therefore we don't need additional condition so therefore we don't need this additional condition and we can simply get rid of it if I modulus 2 is equal to0 then we add the number to even and else we add it to odd normally when you have situations like this we can use the conditional operator where we have the question mark followed by the colon but in this case we're actually doing two different assignments we're either assigning into the even or assigning into the odd so there's no room for the conditional operator so at this point we should have all the even and odd values from zero all the way to 20 inside our two lists so then we can now just print both the list out so we can say printing even numbers and then we can have a for each Loop that goes v item inside our even and then we can do a console Right add some inst string interpolation and then we can say item followed by space then we can print environment. new line just to give it some space and we can say printing odd numbers here we go and then we can just take this exact for Loop and copy it down instead of saying in even we want to do in odd and this exactly the same since the variable name is exactly the same let's try run the code there we go it's got zero all the way till 20 and you can see it goes up in twos hence all even numbers and we also get these going up in twos except it starts from one and this covers all of the odd numbers and if we change this number up to something like 50 then the list will just grow and they Cod just still work okay you can see that all of these numbers are still consistently even so now that our task is actually complete let's just have a little recap so the reason why we're using lists and we're not using arrays is for this exact nature if we have 0 to 10 then we can almost work out how many even numbers and how many odd numbers we can have we can manually count we have zero and then 2 4 6 8 and 10 and then for odd we have 1 3 5 7 and 9 so we know how many numbers exist within here but what if we just change that number to 50 then now we have a lot more odd and a lot more even it's impractical to type these numbers in and then to Simply count them in your head and then make an array length based on that position that's a bad solution because not all cases you're going to have the flexibility of Simply typing in the numbers like this and Counting them yourself these numbers could be something that typed in by a user or something loaded for something external like a text file you need to understand that these values can be generated from anywhere and if you just type them in then it provides an unrealistic expectation of how to write some programs so what you have to bear in mind in situations like this is you simply don't know how many even and how many odd numbers will be appearing during this range so you want to use a list so it as dynamic as possible we have two lists in this case one to store all the odd numbers and one to St all the even numbers we don't initialize them with any sort of capacity we just keep it empty for the exact reason we don't use an array we Loop through from zero to anything we don't even have to Lo from zero we can also just start this at 100 and go all the way to th000 it really doesn't matter what our number ranges the only thing that matters is that we have a list that is going to be dynamic and then we can calculate whether the number is odd or even and add it to the right list how this works is we use I which is the number we're currently up to and we calculate the modulus of it to check the remainder if the remainder is zero then it must be even as it's divisible by two and if it's anything else than Z zero which you can only ever be one in this case when using modulus 2 then we add it to the odd list after this followup has run now our odd and even lists have all the values that they should have and we simply just write these two blocks are exactly the same just print the even numbers and print them out print the odd numbers and simply print them out to the screen and that's it and if you run the code it might get a little bit crazy in here but as you can see these will actually work if you pick any random numbers you can see that they're all divisible by two and this same thing goes for odd you can see that they're not divisible to cuz they're all odd so in this exercise we're going to cover a little task I like this call this task an array of multiples so we want to Define initialize two integers and num into length so in the case of this example we have a number seven and the length of five so what this will do is it will essentially give you the seven times table but only the first five numbers 7 14 21 28 and 35 we take the first number which is Nome which will give us the multiples and we take the second number which is the length and that gives us the size of the array so we create the integer array with the size of length Loop through the array and insert the loop count Times by because this is 1 * 7 2 * 7 and so on so forth until we reach the length and we place into the array and then finally we paint the array just to give us these values out to the console all right so let's get started we can have it into norm and make it equal to seven and we have it into length and make that one equal to 5 now the defined initializer two integers let's create the int array with the size length int array result equals new int and we want size length after that we want to create our for Loop now this is the tricky part if we try go from zero all the way to result. length then let's see what happens so we want to start result I you want to make that equal to number which is our array of multiples Times by the value that we're currently up to now let's print our array using for each Loop to see the value so we can say a v item inside our result then we can have a console right that just prints one of them at a time so we can say item followed by spits now let's see what happens when we run it so we get 0 14 21 and 28 and as you can see these are the first four numbers so we're close what we're nearly there because our array starts at zero and it goes to the length which in this case is going to be 0o to less than five which will cover the positions of 0 to four with these positions it's going to do 0 * 7 1 * 7 and then get to 4 * 7 and not actually get to the fifth because we're starting from zero so alternatively what we can do or what you think you can do is change it to a one and changes to equal to so now what it's doing is it's going from one all the way to five which is still covering the same amount of positions it's just one index forward so now if we try to run the code then we get a runtime exception and the reason for for that is it's trying to access position number five if we hover over I we have five and if we hover over the result we actually have some of the right values except it's trying to get to the fifth position and it's not working the reason why the zero index is actually zero is simply because that's the same value as the default value because our for Loop started at in I it's actually only starting from here and going down so this calculation is actually correct but it needs to be back one we need to start the multiplication on IAL 0 but our for Loop needs to start on IAL 1 so we can get all the way through so we have two ways of doing this we could say IUS one so even though it goes from 1 to 5 it's still assigning into the array using 0 to 4 so if we run that we can see that that will give us the desired result alternatively what we can actually do instead of doing IUS one inside here we can define a variable called counter and make it equal to zero we can change this this to counter and we don't need to change the multiplication because that's already going from one to the length which is 1 to 5 in this case after the follow is run we need to remember to increment counter so there we go we have the desired effect another hack if you're interested if you have two variables that you want to increment inside a for Loop you can see that we already have I ++ in here which will increment it by one and we want to increment counter by one as well every single time it loops around what you can actually do is remove this and you know how these are broken up by semicolons that indicates that the section has ended the first section is for declaration the second is for the range and the third is so you can increment the variable or decrement it when you trying to increment two variables inside a for Loop instead of placing a semicolon here and type in the next one you can actually place a comma and do counter Plus+ what that will tell the for Loop is every single time you go through you want to do a series of these actions and because we have i++ and counter Plus+ then that's going to work exactly the same way it just prevents us having counter Plus+ down here and we can move it inside the for Loop just so it doesn't for us and it looks a lot cleaner cuz you can clearly see that every single time we loop around this for loop we're going to increment these two variables there we go so let's try to put some different values in here maybe make this 10 and we can have 10 on both which should give us the first 10 numbers there we go from 10 all the way to 100 let's have a little recap so we're essentially just making an array that will give us back all the multiples so it's like a mini times table but the fact that we're doing it dynamically using our array is quite important what you can do if you wanted to is to extend this program you can ask the user to type these into the console and then convert them and use them right now we're just statically typing them in and that's not really an issue since the main focus was doing this for Loop if you wanted to you could ask the user and you can type these values in so you don't have to change them every single time you compile so now we've got the number and the length let's make our inter the rare call result and initialize it to the length we set up this counter so we simply didn't have to do I minus one here so it looks a little bit more intuitive we start the follow from one and go to the length so we can access 1 to five and the reason why we want to do 1 to five so when we do our multiplication it doesn't start at zero these two are going through the exact same amount of indexes 1 to five is five numbers and 0 to four is also five numbers so when we do our multiplication we want to start from one since the timetable normally starts at one and we go to the length the reason why we're using the counter is so we don't have to do IUS one in here and it breaks up the logic a little bit and it looks nicer with our counter we start our counter at zero and instead of incrementing down here we use this fancy comma and we can say we want to increment I and counter every time the for Loop goes around so we don't need to include the counter increment inside the for Loop and this one line is pretty simple we say result the index of counter which will start at zero which is the start of the array since it's zero base and we say that's equal to the number and the number is going to be a fixed number since this is the multiple and we say number times by I and in this case it goes from one all the way to the lth so we get essentially the times table and at the end we just use a simple for each Loop that will go through all the items inside the result array and just print them out to the screen with a comma after each other using console. WR just so they're all on one line this is the start of the function section functions can also be called method they are used interchangeable in the introduction we discussed dry which means don't repeat yourself and the whole point of dry is so you don't have multiple sections of code that do basically the same thing you want to wrap it around in a function functions are used to improve the readability of your code and the reusability of the code as well having multiple section code that are basically exactly the same can be more prone to errors if you wrap them round and place in One Singular function you can make sure that the error prone and then wherever you use it it will be error prone as well if you have to copy and paste and tweak some code then you're actually exaggerating the amount of errors that could occur and plus it makes your code look a lot cleaner and the structure a lot better since you can name the functions so let's take a little example we have a static void main straight into here this is a function or a method and these are the parameters for the function The NET Framework expects every C program to have a main function with a capital m and it needs to be a static and avoid the parameters don't exactly matter we can also remove them and it won't be a problem the only thing that matters is this needs to be called main if we drop the lowercase on it and try and run the code then we're going to get a build error program does not contain a static main method suitable for an entry point so if you change this back to M and run it again and then it works fine so that's one thing to note about The NET Framework is you need to include the main function otherwise the program won't run and it won't even compile so let's take a look at how we can use this we can have something like a console right line and we can say welcome to my program this is a line that we're probably only going to use once but let's say this is welcome in someone's name welcome AB let's say you had this in your software in many different places you don't want to be recalling this or retyping out this message in case you type it wrong the fifth time and you get a error of course this won't be a syntax or a runtime error it'll just simply be a logic eror because it's a typo so in order to make sure this typo never occurs we can actually make another function so outside of these curly braces and just still within the class we want to create a new function so we want to follow this exact same approach we can say static then viid and we can call it welcome message and we don't need to give it any parameters cuz we're not really going to give it any values just for now now that we've made that we have no syntax errors and we can run it like this except of course there's no body so let's place our console right line within here now if you run the codee nothing is going to happen and the reason for that is the code will still execute in the main we haven't called this function inside the main we've defined it and called it welcome message and we've gave it the contents but we haven't actually made use of it and you can see that when it's highlighted in a darker color that means it's not being used as it says here private member welcome message is on use so now we can simply type in here welcome message followed by an Open Bracket and then a close bracket to denote the parameters that we're going to give it and of course in this case there is no parameters and then we close the brackets and add a semicolon now if you run the code you can see it says welcome abber so just to go over some of these words that we're using static means that we can access it anywhere and everywhere what I mean by that is we don't have the keyword new just before this we don't need to make a new instance of the program class in order to access this so what that means is when we make future programs we're going to have some functions inside our class inside the class you can actually denote if a function is going to be static or it's not going to be static you don't have to specify is it static but this won't let you call it from here because it's unaware where this function is coming from an object reference is required for the non-static field method or property because this is static you need to reference something else from a static nature all static means is you don't have to create a new instance of this thing in order to use it we'll see different examples in the future where you have to create an instance in order to use something so let me just show you quickly if we have a test and I say static void something and we can just print out nothing to the screen and let's try and use this so because this class is outside of the program we have to use the notation test Dot and then it should be available within here and the reason why it's not is because you need to insert this public word just before it and public means everything has access access to it and static means you don't need to create an instance now if I type in the dot again you can see we can now see something and the reason why we can see something is because this is a static now if I remove the static word then you see that we'll get a compile error because it doesn't know where this is now if you don't use static you need to do this you need to say test test equals new test so you make it instance of the class and then inside test then we get the something so that's the difference between static and not static essentially it's accessible from everywhere but if you don't want to be accessible from everywhere then you can just simply remove the static word and the user will have to create a new instance before they can use it so this is what it's like without static and this is what it's like with sty don't worry if you don't understand this too much this was just a quick overview but I have a dedicated video later on in the course so don't worry too much about it so now that we've made a function and we've called it successfully in the main and it's printed out to the console so when we're declaring functions we want to specify what return type we're going to have we have a static void Main in here if you hover over main it says void which means at the end of this function it doesn't return anything hence it's void if you have a look at something like an inter. trass and we open the brackets you can see that it takes in a string and it takes in an integer out parameter it also returns us back with the booing so we can have something like 1 2 3 out in result and then it doesn't actually complain about anything but what we can do is also just store this into to a bu success and then print it out to the screen there we go so it says it was successfully true if we remove this or whether we keep it in or not trip pass function doesn't actually complain but the main point here is it defines back a bu that means at the end of this function it will always return you back with a bull and it's up to you if you want to make use of it and you can alternatively you can place this straight inside the console right line and get the value printed straight to the screen or you could wrap this around inside an if statement like we've done in the past Etc and make use of it that way and have the result being printed out inside here the point is you have functions that return something and functions that don't if you remember that we had the array. copy for example you'll see that they have void here because they just apply a function to something but they don't actually give you something back this is the difference of having something like this a string test that says hello and then you can do test. replace and then you can return you back with the string and it says here it returns a new string whereas when we had a string builder for example and we did string builder. replace you can see that alloy does say it replaces a new string Builder you can type anything inside here and it will still affect the current string Builder it won't have to do SB equals s SP replace as you would need to do here because this returns you back with a new string and if you wanted to replace test you would literally have to say test equals test. replace with something like a string Builder all the array functions you don't actually have to do any of that so you can say array. empty and it'll just return the empty array and the ones that we used before are things like equals and that will give you back a Bool because that's determining whether it's equal or not but if you're doing functions like sort for example and doing things like reverse it just simply applies the data but it doesn't return you back with anything so you can literally just call it inside here put your array in the brackets and it'll use it happily now depending on your user case you need to define whether or not you need to use a return type or not for now let's just cover void which means it won't do anything so let's just Define a function static void create and print an array open the brackets close the brackets and we can have it int numbers make it equal to new int with a l three and let's just have 0 1 and two inside here as the initializer let's just do a for each VAR item inside numbers and then just do a console right string interpolation and just have item Follow by space and now that it's dark gray because we haven't called the function so let's make use of it at the top of our code and let's run it now you can see we get 012 printed to the screen and if we make this into a five and simply just add more values in here and then we run the code you'll see that now it all update but because this doesn't return us back on anything and we don't actually use the integer array outside of these curly braces it's not actually available up here numbers won't be accessible inside here because it's simply not within the scope numbers is only available within this curly brace and this curly brace which means when this function finishes numbers has now been deleted from memory so you can't access it after this line void doesn't do anything it simply just does the contents of the function and as soon as it reaches the bottom that's all that happens you can have another function defined that can return a value like I said with in. trass for example at the end of the function you'll see a word that says something like this it will have return and then return back something followed by a semicolon and that will dictate that as soon as that function is done it's going to give you something back now we're going to cover that in the next video but for now we're only going to cover void functions so we can have something more obvious like a static void welcome message and simply just do a console right line welcome to my program and we don't need to return anything here because all this function will do is simply print out a welcome to the screen and we can use that just before the print array so we can say welcome message Open Bracket close bracket and then a semicolon and hit F5 to run and there we go as you can see our main is really tidy now it gives us function names that tells us exactly what's going on we're creating and printing an array and then then welcoming the user to the console and then having a console read line at the end there isn't an awful lot of void functions all you need to know is that when you create a function you need to give it a return type it returns back a certain data type or it simply just doesn't and depending on what you want to do and what you want to achieve with that function really depends on if you want to return a data type or not in the case of these since they're just doing something and then moving on you don't actually need to return anything by it with in. tripath you want to make the function is executed successfully so when you use in. tripos you can see that returns back a bull and the bull determines whether the conversion has been successful and based on that return value you can determine the next steps of your program if all your function needs to do is provide some sort of functionality and then quit then that's fine and avoid is fine but if you need to provide some functionality and then also return a value then you'll need to specify the data type in here which we'll cover in the next video so far we've covered a void functions but we haven't covered return types void functions are where the function just does something but doesn't actually return anything hence the name void let's start with an example if you have a static void print introduction might want to just return back your name after you've printed this line it's going to print it to the console and that's all it's going to do there we go let's say there's a situation where you actually want to use this inside your code you can actually set the console's title by typing in console. title and type in your name inside the quotation marks or you can type in anything inside here if you run that you'll see Abra is in the title of the console right now and that looks pretty cool what you got to realize is now we have two references to the same value now at this point we can actually do something better we can type in static string name equals abber and then instead of using abber in here we can say name and instead of using abber in here we can also say name and they're both using this variable and if you run the code now you see that the same output will happen you have ABA twice both both in the title and both in the console output now the problem with this approach is you're actually making use of a global variable which we do not like in code in situation like this you shouldn't need to make a global variable because there are ways around it so instead of having this which has a print introduction and we've got the name used in there but the name is coming from here maybe we can use this somewhere else so let's say we make another function called Static and instead of void we want to actually return back a string so we can say string and then we can say my name or something like return name or anything you want just make sure you give it a meaningful name so it dictates what the function is trying to do so this is to return the name and the reason why there's a red underline is it says not all called P return a value since we need to use our keyword return now that we add some empty codes and the return it's going to execute fine and the compil error is gone so obviously we don't want to just return nothing we actually want to take this arber and return in here so let's get rid of our Global variable and let's see what we're going to break so we're going to break these two references to the name variable and simply inside here we can actually just call return name and then here as well we can call return name and what this will do is inside here it will execute this function and then return the value in here if this is too many steps for you you can have a string name equals return name and then simply use the name inside the brackets these two lines are doing exactly the same thing except this is using a variable CU we're starring it first and then we're using it whereas if you place it straight inside the brackets that's just going to store it and use it immediately and there's no additional variable but don't worry too much if you're going to do this notation because an extra variable in this case doesn't really matter because as soon as this function is executed the variable used to run this function gets deleted since it's inside the scope of these two curly braces so now if we run the code you'll see that again we have abber and abber but now what we've done is actually controled everything throughout here so if you want name where to change or maybe this changes in different circumstance based on the user that's logged in then you can simply have the same thing now printed in two different locations in the title and in the console output and it's actually coming from one function so we can have a return name and we can make a static in now can say return age and then we can have simply return 23 and that's our name and our age being returned I change us back to abber and then instead of the print introduction maybe we actually want to print a little bit more than the name then maybe in the title what we can do is have string interpolation wrap the return name and maybe put a hyphen in there and then we can say return age so if run the code now you can see we have ABA hyphen 23 so maybe that's the title of our console but then in the introduction we can use a bit more than that so we can have int age equals return age and then in the console output we can have something like this hello my name is name and my age is age and then after we've compiled that together we can place the output inside here there we go so we're using the name and the age inside the console title and then we have this function that runs to get us back the name and the age and then we're using it using string interpolation of course these four lines can be all squished into one you can simply take this dollar sign let me duplicate this line you can take this and paste it straight into here and while you have name we can have our return name and while you have age you can have return age and that will actually rule out all of these lines and you can wrap it all into one there you go and if age were to change like I said before you can simply type this number in change it and you can see in both cases in the title and in the console output it has officially changed functions can be very helpful to reduce repetition in code let's show you an example if you had three sections where you said enter a number and you had int n one equals convert to in32 and then we add a console. readline and then you had this section and you wanted to do num two and you had this section again and you actually wanted to do num three now at this point even though these three are actually identical you want to be using array in this case so you could have int numbers equals new int Square braet 3 and then here we could say numers zero numbers one numbers two and then we don't need the ins because it's already been defined and then we have them like this but because again all of these three sections are exactly identical we can actually run a for Loop that goes from numbers do length and then we can place one of these straight inside here and then change this to I and now we've achieved exactly the same thing but we're not actually done yet so if you run the code and we do 1 2 3 now we stored all three numbers so we have enter a number and then we have the console read line and maybe we can actually make these two lines a little bit shorter so let's make a function static and because we essentially want to return an integer we can say static int read number from console and then if we take these two lines place them inside here and because we need to return back an integer this is the value that we're going to be returning so instead of assigning this position to something we'll actually just immediately return at this point so instead of doing this line now and instead of doing all of this we can simply make this into one line of code read number from console so every time this will execute it will jump into here print out the value enter a number the user will type it in it will read it in convert it to an integer 32 and this will return back the integer that the user typed in and then that will return it back to the console and essentially replace this so if the user is typed in five then it essentially replace this with five store it loop around and if replaced in 10 the next time and then you replace this with 10 essentially and then that gets started inside and so on and so forth until until all the positions have been complete Let's test that 1 2 3 and it still works okay of course I'm not actually printing the values out to the screen so if you wanted to see that quickly for each can have our item inside our numbers and then do a console right with some string interpolation item followed by a space let's run that one two and three and there we go we get one two and three of course you can make these functions and they can return any bits of data that you want you can even have something like an INT array and we can say create random array and then we can create an array call numbers make that equal to new in square braet 3 and we can actually give it the values of 0 1 and two and then just at the end here we can actually just return numbers and then just in here we can have an INT array and we can call that new numbers since we have numbers above just above here and then we can make that equal to create random array and because this returns us back with an integer array there's no compile arrays inside here and we can have a for each follows the exact same approach as the one above new numbers console right line into a console right and then have item followed by a space now if we print these both out you can see that the zero one and two actually comes from the new one it's just we have two console right right next to each other so there's no new line separating them so if we just add a console right line here one two and three and there you go 1 2 and three comes from the three inputs we just typed in and 0 1 and two actually come from the function we've just created of course if you don't like this notation then what you can do is you make it a lot easier you don't even need to make a new variable you can actually just return the integer just like this so if we place this straight inside here actually just make it on one line just so it looks a bit neater then there you go we have our entire function reduced in one line the goal of functions is to make them do as little as possible if your function has two different things it's doing or more then you should break that out into into another function for example if you had a function that did two distinct operations one was a conversion and one was a calculation then you want to split out into two the first function should be the conversion and the second function should be the calculation and the reason why they're separate is because if you want to reuse them as a pair then you won't be able to reuse each of the pairs if you wanted to have a calculation on its own then you can't do that if both functions do the same thing for example you could have a static and it just could be something let's just call it VI and it could just be test for example and if you had the conversion here and then if you had the calculation in here then you need to split this up into two different functions you want have static void conversion and static void calulation if you wanted to use conversion or calculation separately you can't because now it's in this pair together so if you wanted to use them separately you simply can't it's best to keep functions on the RW anywhere just so they have a single purpose so you can give them a name cuz as you can see here we can't can't give this an appropriate name because it's doing more than one task this is doing the conversion this is doing the calculation and this is doing multiple things this could be doing something if you have to think too hard about the function title then you might be doing too much within each of functions these are very easy to be able to decide what they do cuz this one converts and this one's going to calculate reading number from console if this was reading the number from the console and doing something else then it's going to be a bit of a problem because now you've got a bigger name you don't want to be doing reading number from console and and something else cuz then your function name gets also too big and you got multiple dependencies so best thing to do is to call them accordingly and keep them as short as possible so let's say we wanted to make a function that added two values we can have a static int call it add and then we can return 5 + 5 now this function is a little bit redundant although it will actually work so if we go back to our main and we do a console right line and actually print the value of ADD and we go through our function then we see we get the value of 10 which is indeed 5 + 5 but since this 5 + 5 won't change it's always going to be 5 + 5 this is where parameters will come in which we'll cover in the next videos parameters are a way of being able to give the function value so these two can be actually changed there's no point in having an add function if the only ability you can do is add 5 + 5 because you may as well just return 10 at this point so I covered a lot in this video and there's lots of different functions that do different things of course there is quite a lot of lines we're up to 87 this is probably the biggest project that we've wrote so far and even though this is not really a project it's just a bunch of functions that do little things that are made for demonstrations so let's have a recap so first here we're setting the title as a result of return name and return age we can actually take this and develop this further if you want to we could actually say return name age pair and if you wanted to collapse that inside one function then that could be really easy you could say static string return name age pair and then you can have return and literally the exact same line above you can have return name followed by a hyphen and then you can have a return age and then end the line like that so that just concatenates the two values that are returned from these two functions but the point is you keep them all separate if you were to type in very statically inside here AB 25 then obviously like I've talked about above then you're going to have duplication of data and of course we're going to use this name inside something like here and as you can see this name age pair is actually not applicable when it comes back to this format so it's always best to keep these two separately so if you bring it back and we can actually keep it like this now instead of having this code we can actually say return name age PA now will give us the same value at the top of the code it will have ABA hyphen 25 so that's that bit in our print introduction If We Hold control and we actually press on this function it will actually jump us right down and then if we press the back arrow top left we can go back to it there we go and then click forward so in this function we can break down all of the return values into string variables we have a string name equals return name an inage equals return age then we have a string input that concatenates them both together hello my name is name and my age is age and then we print out to the screen or if you wanted to we could wrap all four of these lines straight up into one we don't need to assign these into variables although it does help the readability if you keep them separate but I prefer to keep it like this since I'm used to this notation we can place return name straight into there which will get rid of our name variable and the same thing with age which will get rid of these two variables and of course we're actually storing the string value before we printing it so we could just take all of this and place it straight instead of here scrolling back to the top this little section was demonstrating how we can use integer arrays to read in all the values from the console but wrap it around in a function so before in here you would would have something like a console right line you'd print out the value to the screen that would say something like a ter number and then you have on the next line a convert to in32 and then after you converted in 32 you'll actually start it straight to numbers but because this is going to be the same thing for inster all the numbers you can actually wrap this around in a function so if we hold control again and go to this you'll see that them two lines are very simply placed in here console right Line enter a new number and then convert in 32 based on the console read line and then we're simply just returning that back ready to be stored in the index of the numbers array and then straight after that we're just printing out all the values to make sure it's worked and that all succeeded fine here I was just demonstrating that you can have different return values and it can literally be anything so as you can see here if you hover over create random array it's inside the program class it's called create random array and it returns back an integer array so that's what we're sign into and if we hold control and click on this again you can see that all this simply does is returns us back back a three length array with 0 1 and two as the array positions and then if we scroll back up when we execute this for each Loop then we're simply going to get 0 1 and two just like that since it's a console right and it'll be on the same line with a space after each other this demonstration was slightly theoretical I was saying in one given situation a function should only do one task if your function converts and does a calculation at the same time then these are actually two different things you should split them so you use the conversion in this step and you use the calculation in this step if you wanted to convert something or calculate something in the future then you can only do it now because we've separated them whereas before if you have them both inside here then you simply can't do one operation because you wrapped it around in one section the same is true when I was discussing this earlier on if we kept this name pair is the only way to access the age in the name then it's going to mess up when we use it in here and then we're going to have a duplication of data but because we separated the name and we separated the age we can use it in this function and we can use it in this function and it doesn't interrupt anything this simply Returns the name this simply Returns the age and these two functions make use of them if we had something else underneath there were another function that depended on the name of the ede then again we can simply use them if it was restricted to this function then it's going to be a problem using it in this function or any future ones and finally just to finish off add function and all it simply does is return 5 + 5 and I was saying as of right now even though it returns back a value it's kind of pointless CU you may as well just return back 10 since it's doing the same thing the reason why included this function is that we can set it up and start planting the seeds to understand why functions exist and how to make use of parameters what a parameter is is it lets you put things Within These brackets so you can give this function some data so if you have an in. trass for example these things that we place ins inside the brackets are actually the parameters so we have a string s and out in something and that's how the parameters work on our Tri pass function and just to show you this is how it's actually wrote It's a Bo and then it's called trip pass and it takes in a string s and out in result then we can make this static and I know it's give us an error because we don't have the control path if we just use result and assign it to zero and then return back true you can see that the compil error is now gone on and as you can see here it says bull trip pass string s out in result and if we actually try and use the trip pass in here and press the brackets you can see that these parameters are exactly identical to parameters that were inside of the tripar coming from the integer Library so in the future we're going to study how we can use parameters to pass data inside our function but just for now know that this function is essentially pointless because it's only going to return back 10 and this function will gain the functionality it needs on when we start adding parameters this should essentially be add five + 5 except this is kind of a pointless function because we already know the value is going to be 10 but again this is just helping you understand why parameters are very essential to functions we've covered how to create a viid function and a function that returns a data type but now we want to create a function that gives it some sort of data you may not realize it but all these functions that you normally use like console right line you're actually inserting data consistently into all of these functions if you hover over console right line you see his void console right line and right now there's an open bracket and there's a close bracket if we delete this bracket and reopen it you see there's 19 different ways you can call this function and as soon as you start to type a string you can see we have a string format and an object if you need to and if you type in another string you can see it says string value this string value is actually a parameter If We Hold control and press on right line you can see all of the different functions right here this is the most basic version that just inserts a right line character to the console and then these are all the different parameters that you can give the value of course you can't double click and view the source code because this is hidden inside Microsoft's libraries the values that are placed inside these parentheses are actually called the parameters this is known as functional overloading which we'll cover later on in the course basically that means you can have the same name function but give it different parameters and you'll see why this is helpful later on down the line so let's close this tab in the top right hand corner and let's bring back out code so now that we've passed hello into this function that's was actually given this a string value parameter and that hello is going to get passed straight into the console right line so then when we run the code it's going to print it to the console so let's create our own function with our own parameters so if we take the function I had last time it was static int add Open Bracket close bracket and it simply returned 5 + 5 which we all know is going to be 10 so if we place add inside these brackets and we run the code we should get 10 return back there we go so of course the this is a little bit pointless since it's always going to be adding 5 + 5 there is no way we can change this without the use of parameters so in here we can actually just do what we do when we normally declare a variable we say the data type int and then the variable name and then if you want to add multiple parameters you can simply add a comma so now we can say int a and int B and you can see now we've got a syntax error because it expects us to have both of these values inside if you hover over it there is no argument given that corresponds to the required formal parameter a and then if we insert a by having five for example and if we hover over it it complains about not having B so we can do comma and then do five again so just this on its own is not actually going to do anything we're actually giving the add function the values of five and five and place them inside a and inside B variables these are now known as local variables and they only exist in memory between these two curly braces as soon as this function is done these are deleted from memory and you can no longer access in a and int B you can't just do something like a inside here and think that this can be used up here these are in two completely different Scopes this is one function and this is another function and they're completely separate from each other when you type in five and five it goes in order so int a is the first one so five gets placed into here and this five gets placed in a b so now that we need to make use of them we can simply change this to a and change this one to B now if we run the Corde we should still get 10 but now our function Works a bit better we can give it a set of d so if we actually just put zeros instead of here then we should get 100 returned perfect so now that we've figured out how to do this let's have a look at different ways that we can make use of this function so let's say we had a situation where we did console right enter a number and we add int nor equals convert to in32 and then converting the console do read line and let's wrap this inside a function so before what I was doing is simply just returning back in int it was static int read int and then we took these two lines and place it straight inside here and remove the fact that we have an integer and simply just change this to a return and what this now will say is let's output enter a number to the console let the user type it in inside the console read line and then read it in convert it to an integer and then give it back to whatever calls it so now we can get rid of this and get rid of this convert and simply just type in read in inside here and after the line let's just print it out to make sure it's worked okay enter a number 10 press enter and we have 10 again and that's fine except if we want to use this in another case for example if you have num one maybe we don't actually want to enter a number maybe this time it's going to be enter an angle or something of this sort so what we can do if we undo that we can actually introduce a string message and what this will do now is actually specify the message that we put in here maybe there's a situation where we always want to enter something so maybe we can just replace this and put a string interpolation and wrap this number around in the curly brace and replace it to message so then in here we can say enter a and then we can pass the string variable which will get placed in here so if this is a number then we can type a number and maybe this is something like an angle and then here we can type an angle so we have 10 enter a number and then there you go it says enter an angle then we can have 100 and that's working as well alternatively if you want to specify the entire message then you can remove these and keep it like this and then in both of these situations we can say enter a number and copy that down like this and make sure you put the colum at the end followed by the space there we go enter a number 10 enter an angle 20 maybe the situation where this text actually changed and you just want it to be angle and if you run that again then you'll see that these are completely different now one says enter a number and one says angle but this gives us a lot of flexibility in what we pass in if we keep it as enter a and then let the user decide on what this section is then you rule out any opportunity to be able to do that option if you wanted to to prevent the colon in the space always being at the end you can actually just add that in manually if we bring back the string interpolation we can say colon followed by space so you don't have to remember to always put that in there we go so that's doing the exact same thing and we're actually just reducing the amount of repetition because we have to remember to put a call on Follow by space inside here we might just forget it and then when you leave it like this then the chord is going to look ugly because it looks like this and it's all stuck together so let's make use of these two functions and let's see if we can write a really basic calculator we can say int first num equals read int and we can say enter first number and then duplicate that down change first to second and then change this also to Second and then inside a console right line we can actually have the add function and we can type in first number and then we can type in second number and if you don't want to call the function inside here you could actually just make another int and we can say int result equals add and just bring this line over to here and then in the console right line you can just print the result there we go so we read in both the values execute the add function and then return it back to the user using a console right line so these are the other ones and then here they are so if we do 50 and we do 50 again and you see that I've messed up because we have double colums now so although our calculator did indeed work let's just go and correct that so we can take these off now because we added it inside here 50 and 25 we should get 75 perfect so now we've made a little basic calculator by simply making use these functions and if we just expand this just to show you what it would have looked like so we go in from this and we place our message inside to here and then we have our convert line just like this and then if we duplicate that down we can change this to second number and then to second number and then as for the result we can say first n plus second n there we go you can see the code is drastically longer and is a bit meaningless to have duplica code this is literally the exact same line in both of these sections except for the fact that this ISS first and this ISS second and we're starring in first and we're starring in second so let's undo that and get back to our more efficient code there we go you can see that these three lines are considerably shorter and easier to read this is telling us we read integer here is the value and we want to return it inside our first Nome and so on and so forth let's have a look at another example where we can make use of this so we can have a string called name and we can read this in from the console console. readline but we need to Output a message so we can have another console right and we can say enter your name and then we can have this twice and we can do enter your age and then have an INT age but of course we don't want to be using this approach and putting a console right line inside here with a convert in 32 because although this is actually technically correct now we're UND doing the point Val function so let's change this into our readint and then as for our message well we have the message right here and again we don't need the space colons let's remove that and then as for the name we can actually do this differently so this is actually going to do a string variable so what we want to do instead of having read in we can have another function called read string another string message parameter and then do exactly the same thing have a console right and we can place string interpolation and place a message inside here followed by callon space and then we can just simply return the console. readline there we go and instead of doing all of this we can actually just put our read string inside here and then place our ENT your name inside here just without the call on Space because we don't need that so now we' reduce this section to two lines as well so now what we can do is have a string details and make that equal to a function that we're going to use now we can say user details if we want to give it the name and give it the age and that will give us back a string that we can print to the console so we can say details so let's go ahead and make use of this function so we can have a static and it's going to return as back a string CU we're placing it inside the string and then it's going to be user details and then our name is a string our age is an INT and then inside here we just want to concatenate them two values together so we can say hello my name is name and my age is age and because that's returning us back with a string we can make use of it inside string details or we can place this straight inside the console right line let's leave it as a function call assign into string details and then print out to the screen let's just skip over these sections enter your name AB enter your age 23 and then there you go hello my name is abber and my age is 23 so this is how we can make use of parameters and inside our functions so we can actually give it some sort of data that's meaningful if you didn't use parameters then what you're going to have to face is for example we showed you with this integer if you don't use parameters then you're going to have situations like I showed you before with this integer function it returns back an integer but it only gave us the value of 5 + 5 I mean technically you don't need to return anything you can actually just keep this avoid and just wrap this around in console right line the only issue with this approach is you don't have any option other than to print out to the screen or if you didn't want to print out to the screen and he simply just wanted to return the calculation and then store it inside another variable this doesn't give you the flexibility of that so we change this into an INT and instead of returning it back to the console we just return back the pure value and then if the user decides that they want to print this out to the screen that's fine like here we've made a decision that we want to print out let's just say we had a variable that said in calculation then we place that inside but we actually never wanted to print it maybe we kept it like this and then use Cal for some something else down below or maybe that was something like storing inside a database not everything will be printed out to the screen for the user to see the best thing to do is return the values in their purus form because you never know what the developer or the user is going to make use of that data later on down the line keeping it it's purus form is the best way possible for example in this case we're actually reading back the integer and then print it out to the screen but in this exact case which is the best case scenario that I just showed you we're actually making use of first n and second n but first n and second n and never actually print it to the screen it's always just used for the calculation if we use console right line to print out first n and second n then we're not going to be able to use it inside our calculation and therefore our very basic calculator is now being rendered pointless so read in and add all return back values that we can use in their purest form and that is the whole goal of parameters so now that we covered parameters that are always going to be required let's have a look at another concept called optional parameters so we had a static int add and we had int a and int B for example and then we simply just returned a plus b like we used in the previous examples if we have an INT result and we want to call that function and we give it the value five and five and then print out to the screen everything runs okay because we've added in exactly what we expect let's say we don't actually have this additional five of course this doesn't make any sense cuz we meant to be adding two numbers but just humor me for a minute then what this will do is says there's no argument given that corresponds to the parameter B now of course this is a problem because it's a red underline which means if we try and run the code we're going to get an issue let's say you creating some sort of system that if you entered both values it uses both values but if you only entered one it automatically set the second value to something else and we can achieve this Behavior using optional parameters so an optional parameter doesn't exactly mean quite optional it kind of just means that it's going to be optional but you can also give it a default value this will always add two numbers A and B even if we make a or b optional it's going to still need two numbers to add in order for the function to run so in order to make a parameter optional let's just say we want to make B optional we can type in equals straight after it and actually give it a value so as you can see our syntax error is now gone and if we run the code we should get 55 and the reason why this works is a is now five if you hover over here we can see a is five and then the square brackets around the int B actually denotes that it's optional and it says int b equals 50 cuz we have that here so it's actually using this as 50 and if we don't specify the second parameter then it's practically just doing this which is completely fine so the reason why I said it's not quite optional is because you still need to give it a value of course in here you can use the default keyword in the case of an integer the default value is actually zero so if you just run that code now it's going to say 5 + 0 which is just 5 so it can be optional but you still need to give it some sort of value of course if you're doing a calculator and you're adding two values if you only specify the first one then adding zero to it is simply not going to change it so zero or default is going to be the best user case when you're dealing with default values with integers so another way you can actually specify this is by inserting this thing called an attribute if we remove this equal zero and just before the end we can type in Open Bracket close bracket and type in optional with a capital O and then you're going to get a red underline if you hover over it it says we need to include this extra Library which will import it at the top of our code as you can see here now that this is available it says indicates that a parameter is optional and what this will do by default is it'll give you the basic value for this number so what I mean by that is we can type in here just to show you this b equals and then B and this will just give you the default value based on the data type and as we just said a minute ago that value is actually going to be zero there you go B is zero so all it's doing is saying 5 + 0 = 5 so that's another way of doing it or you could just leave it as I said before you can say in b equals default or in b equals z it's completely up to you I prefer using the default keyword so you don't have to keep remembering which different data types have the default values in the integer case it's zero but I just like leaving the default and we can get rid of this line now let's have a look at different situations where this be helpful if you had a function called print name and we had a string name in here and then we can simply just say console right line my name is and then name this is quite easy to use so we can say print name and then place arber inside the brackets and then run the code and we get abber printed to the screen and that's fine but let's say if we had someone else's name in there as Joe for example then we get Joe to the screen and let's just say as the developer you only want to default this to abber if you you don't actually insert anything so now if you don't insert anything of course we're going to get a compil error because we need a parameter but if we assume what we did here and just follow the same approach if we use default then it's going to give us nothing because the default value for a string is just empty quot which is just nothing but instead of default we can actually specify value so we can say if no one types their name inside the bracket then use abber there we go so you can have this optional parameter that defaults to something and if someone types in jaw or whatever inside the print name function then the default optional parameter is not going to be used since this will be overridden if you have a parameter placed inside here so now the abber is going to get overridden by the jaw because this is actually the parameter that's being used in the function so you've looked at functions with normal parameters optional parameters and now let's take a look at name parameters so let's say you had a situation where you had string name ABA in age equal 23 and string address equals one something Road and then you had a function that would simply print these details out to the console so start void print details there string name inage String address so you have three console right lines that just print out a name value pair just like this and then when you go to call this function what you're going to have to do is specify the name then the age then the address in that specific order as per the parameter show if we try and run the code now we should get the desired output perfect let's say for example you wanted to rearrange the parameters and put Age first you'll see we have a compiler error now because age and name are in the wrong order string name should be first and int age should be second we can still achieve this by using something called name parameters we don't have to stick to this order if we tell the compiler which parameter we're directly talking about so we can say age callon because our parameter is now called age as you can see it's been being highlighted and then after the call on it's the variables that we're talking about so it just happens to be that age is the same value as the edge so maybe we can change this to age input and place input at the end of these so then we can have age equals age input and name parameter equals the name input and the address parameter equals the address input now we can have it like this and to make it look even better you can actually add new lines in here just to break it off like this and this is a similar pattern that you'll see in normal production code putting a space here can separate them out a little bit and there we go it doesn't matter which order that we put these in right now we can even put address first and it'll still work okay and if we run it you should still get exactly the same output it's just specified in a different way so let's just have a little recap to make use of name parameters you don't need to do anything to the original function you just write it exactly the way you're used to doing you specify the parameters in the order that you think is sensible and when you go to call it you can simply just type in the parameter's name first followed by colon and then the variable name that you want to address once you've done that then you can use name parameters you can go back to using the normal function by just getting rid of the name followed by the colon and just replacing all of the parameters using the correct order and the original variables instead of the new notation having Name colon followed by name input so far we've covered functions with no parameters normal parameters optional parameters named parameters and let's look at a concept called out parameters let's demonstrate a quick example so if we call a function called test and we pass in a value and let's just make this work so we can have an INT Norm equals 0 and then we have a test function so we can say static void test and we can say in Num and inside here let's make num the value of five now in this example if we print out num to the screen what do you think is going to happen is num going to take the value of five or is it going to keep the value zero I'll give you a second to think and let's run the code so let's run it and see what happens and if you guess five you're indeed Incorrect and if you guess zero you are correct and the reason why it's not five is because when you pass a num inside this parameter it just becomes a parameter and therefore it becomes a local variable even though these two variables are actually called exactly the same thing you'll see that when I highlight it it only highlights this one and doesn't highlight this one and the same is true for this it highlights these three references but not the ones down here the gome variable is only accessible in each other scope this one is available through here and here and this one is available through here and here therefore if we use this assignment then it's actually doing nothing if we print out gnome inside here num equals num and then we print that we can see that it is assigned the value five but because it doesn't do anything at the end of this function then it simply doesn't get returned back or anything happens to it so let's see how we can make make this in to five when it gets printed out here so the options that we have is we can actually make this vo an integer and we can say nor equals 5 and then we can return num or alternatively we could simply just return five and not do both of these lines so if we run that now then we still get zero and the reason why we get zero is the test function is being called and it returns back an integer but we're simply not doing anything with it so we can say num equals the return value of this function which will be five and now if we run it we should see our five perfect now this is a little bit cumbersome and let's say you wanted to return a value and return back another value at the same time then what are your options so let me show you a quick example when you're using int. tripod we have a string s an out in result and a bull so what this function is effectively doing is return you back a true or false value to dictate whether or not the conversion has been successful and it's also returned you an out into result and what what this means is you can actually specify integer variable straight inside the brackets so in essence this function has gave you back two values it's gave you back something from the integer parameter and it's also returned back a Boolean variable so let's convert this to code and see what the third option is of trying to return back five over to this so if we just comment out this line and as you saw in the trip pass you simply just need to put the word out just before here out in Num now we don't actually need to return anything in this specific example because we want to just change a num variable using the out parameter but if we wanted to return something separate to the num like a booing like the tri pass did then we have that option so we can return back true but just before we return back true as there's a red underline here it will say that the out parameter gome must be assigned so we need to give num a value we give it the value five because what we're actually doing here even if we double click on this we'll still still get none being selected here cuz the scope is still exactly the same now except what's happening is when this variable gets returned it actually gets put into the variable that it was initially called with so let's fix these compiler errors first so the reason why it's complaining is because we need to give it the out keyword so when we're specifying in Tri pass our first parameter is a string so if the user types in 1 2 3 we put in the first parameter and then we'd say out in result or something along them lines you have an out and then you say you want to make a new integer and you want to call a result see in our case we don't need to put int just like in here because we've already created our num so the only keyword we need is out to follow by space and now of course we're trying to assign this back into an integer which we don't need anymore because this is a booing so we can say bu success equals test out n so we print out Success Print them both the screen now we should have five and true the true comes from the return true and the five comes the num equals 5 so what's actually happening here is we're creating our new integer we're passing it into this function we're also telling you it's going to be an out parameter so this function can still output things to our number variable and then when it gets placed inside here we assign Nome equal to five and then just because we have a bull we have to return true or we can return false of course we can just take this out completely take away the return true and just keep this as test of course in both scenarios these aren actually do anything they're just complete random values it's just made for demonstration so bu is returned back true or false doesn't actually mean anything I was just demonstrating that you can have two return values from one function there we go we get five when we run it just like this so now I've completed this little example let's have a look at how it's used in the real world so before we continue let's see if we can rewrite the tripal function in our code so it's going to be a static returns back a we have a triy pass our first parameter is a string s and our second parameter is out out into result and inside there we can just do result equals to zero and then we can return back true of course we actually need to do conversions inside here if you want this function to work but I'm just showing you for demonstration purpose if we uncomment this line out and have a look at the parameters again you'll see that now they line up perfectly string s out in result and it returns back a Bo which we have exactly the same here there you go bu in. trass string s out in result so that's how this function has been declared of course they're doing something inside the body that can take in the string convert it to an integer place it inside result and then return whether or not the function has been executed successfully so now that we understand how to make an example and how to make the trip pass function ourselves and to give you the Declaration let's have a look at a real world example so if we had a list of string and we had our shopping list that was used from the examples we can have list string and let's just create our own initializer just with coffee and milk inside there we go so now that we've created that we've got our shopping list if you wanted to find something inside the shopping list we have the function index of and what that will do as it says here searches for the specified object and Returns the zero based index of the first occurrence so if we were to search for coffee then we should get return back zero so let's try and run this and put it in the console right line and see what the value is there we go we get zero since it's the first item and if we place milk inside here we should get back one there we go so let's try and rewrite this function into our own code so all this will do is loop around all of the positions until it finds it and it'll find the first one and it'll return us back the index so in this case there's no out parameters but there is a return value so we can also include an out parameter and then instead of assigning the value of minus one we can actually assign the value of true or false to dictate whether or not that we found it so let's write the code normally in here and then let's wrap it around in a function so we can say int index equals minus one because we want it to start a value that we know is incorrect since the lists are from zero onwards the value is only ever minus one then that means it's not in the list then we can then create a for Loop entire equal Z shopping list do count cuz we want to go through every single item inside the shopping list and inside here we want to do a lowercase comparison so we can do if the shopping list square bracket I do to lower do equals and then we want to make that equal to just something that we're going to type in statically so we can just say copy we can make this into a parameter after but this is just for demonstration purposes so we have a bracket and if we found that match then we can say index equals to I cuz the index of the position that we want to find must be up to I cuz that's the one that we've made a match with and we don't need an else inside here we don't need to set an else inside here to make it equal to minus one because if it simply doesn't find it then the index variable won't change its value so it will always stay minus one if it doesn't find anything so after the follow Loop is run let's just print index out to the screen there we go we have zero and if we change this over to milk run it again then we actually have one placed inside here perfect so now what our function is doing is giving us the values of the index if it finds it now if you type in something else if you just add another can let's see what happens then we get minus one and minus one means that it's incorrect and it hasn't found it and what we we can do inside here we can say if the index is greater than minus one then we can say found or else we can say not found so let's run the code now and see if we get a visual representation not found and if we changes back to milk run it again then we get found perfect so as you can see here we're actually checking if the value is greater than minus one but it'd be easier if you had a variable called found and is actually a booing variable so we can make a Bo found and make that equal to and if statement condition so we can say something like index is greater than minus1 which is exactly what we had here a second ago and because this is a condition it's either going to return back true or false and it's going to place the value inside found and then we're going to use found inside here this is easier logic to understand if this is true then it's found if this is not true then it's not found true true false false it's quite really straightforward and very easy and clear you have an index and you have whether not it's being found so let's try and wrap this around inside a function so just as the trip pass does it returns us back with a Bool which in this case will be our found and it also gives us back an integer result but in this case it's going to be our index so let's see what we can do to write this so we can have a static we want to return back the Bo and we can say find in list we need to give it the item we're going to find so we're going to need a string s we need a string s for the item that we're going to find we need to give it the list as well and then finally we need our out int index there we go so let's comment out this code here and let's copy this down into our function and see what we need to do so index has the value of minus one we don't need the integer variable declaration here because we've already declared it inside the parameter so after declaring inside here we give it the value ofus one minus one indicates it hasn't been found since the index are zero based so instead of shopping list we now just have list and list here as well and then instead of having it being equal to milk we actually want to use our s variable and to make it better we can convert it to lower case just so we have lowercase conversions on both sides of the equals if we find a match between the list that we've passed in and the S variable which is our surge term that we've passed in then we assign I to the value of index and then it's still got a red underline because we haven't returned back bu so right now we actually want to return back the found variable so we have two options here we can return back found or we can simply take this and return it back in here we don't need to run this code to see if it's found or not and then store it and then return it after since we're not doing anything else with it we could just return it like this this makes the code considerably shorter because this will just return back a true or false if the index is greater than minus one then it will turn back true if the index is less than minus1 then it will turn back false so let's see how we can use this function inside our code now so we wanted to search for milk so let's just copy and paste this line and let's see if we can get the same output as the shopping list index of so now our function is called finding list you have a bracket and then our string s is going to be our milk our list is our shopping list and our out in index so this is going to return us back with a booing so we can print that booing to the screen and then if we just duplicate that down and we can print index to the screen and maybe using a console right line and just place a space right at the start so we print out whether it's successfully converted or not and we get the value back from it let's run the code so we get true plus the value of one so that means it's found it and it's found it at one index and the previous line before it which just run the normal index of function also return back one so they're both the same let's just get rid of that space so if you change these both to coffee then hopefully we should see the same result but with index zero there we go this zero comes from the index function this true is from our function telling us has been successful and this zero is the index so we can actually take this and put this straight into an if statement so just like we had down here with the found and not found we can say if and then this function call and then we can say found and then the item what we passed in so in this case it's going to be coffee found coffee found coffee at index index and if it hasn't been found then we can just print not found and this is getting an error because we have two indexes up here so let's comment out this line and let's try running out found coffee index zero and you can see these two are the same again one comes from here and one comes from that index we change these both to milk now milk milk and milk then run the code and you see F milk index one if you wanted to just before you pass in here you can ask the user enter an item to search start inside string search equals console. readline and then instead of passing mil in here we can just pass in Search and then instead of passing milk in here we can also use the search variable so now if we try run it again we can type in milk and then we go file milk index one and then coffee found coffee index zero and just to give this a test let's just try and find m not found perfect so let's have a little recap based on this function so initially we tried to assign the value of zero and then print out a normal function and inside test we just had a simple num equals 5 and what this was doing inside is just locally assigning it but not actually return anything and then we said we could assign it and then return it back and that was another option of being able to assign the value to five and then we useed the out parameter which allowed you to pass in an integer when you assign in here it will pass it back into the original call and place it in this variable here so when we print out on the next line it says it's equal to 5 we wrote our own little shopping list for the list of strings and then we called the shopping list function index of and then we actually created our own index of function and made it into a function so just a little recap what's going on here we have a string s which is our search term the list full of the items in the index that we're going to pass back to the user as well as returning back a bu to indicate whether we found found it or not we set the index to minus one so then that completes our logic at the bottom minus one means it hasn't been found since the list is all zero based if this value is greater than minus1 then that means that we found it inside the list since the list is zero Bas and if it's not that and this returns back false then we mustn't have found it because this line would have executed so we Loop through the list we do a lowercase comparison on both sides of the equation on the list item and on the sege term if they both match we run the index and stall the I variable inside the index and then we return whether index is greater than minus one so after we've turned this back from the end of the function we can see once we run it inside the console right Line This is just going to return us back with a true or false value as well as creating our new integer variable called index so on the next line we can use index and print out of the screen this line should return true or false since it's a Boolean return and this variable will either give us minus one or something above minus1 but in this case when we actually make use of the function we can ask a user to enter something get them to type it in and pass that into the function but more importantly when this function returns if it's true we output it's been found and if it's false we output not found and we only make use of this integer variable should this return back true there is no point in printing minus one to this screen because that's what you're going to get if it's not found it's going to look something like this which is kind of redundant because the user doesn't care about this so we don't need to include it when we're printing not found but we should include it when we're printing out the found of course this is just a random example and you might not need to print it out to the screen or you might just do something else inside here you might be searching for something and then you might want to edit it or do something else with it and then you can make use of that index if you wanted to ask the user to search for an item and then tell them what they want to replace it with then you can also do that just as we've covered in the last examples so after after we've covered out parameters and normal parameters let's have a look at a concept called passing by reference so we created interm equals 10 and let's call it assign and we passed it straight into here and we can have a static void assign in N if we say Nome equals 20 if we use a console right line up here then Nome is still going to be 10 because we're not returning it and we're not really affecting it now other ways we can do this is by changing this into an INT and then we can say return 20 and then we don't really need this anymore so we could just say num num equals a sign and then we'll get 20 assign back in there we go or we can actually make this an out into num and then we can say num equals to 20 and then inside here we can say out num we don't need to return back in anymore so we can make this Vol and you see the value 20 so there are different ways that we can assign a variable straight from here so let's let's have a look at another method so instead of having out we can actually use a new keyw called ref and the reason why it's ref it means it's passing it by reference so when you pass a value in through a parameter normally you're actually passing by value and what that means is you're copying this value that gets passed inside the brackets into here and it's making a whole new variable what I mean by that is this might have memory dress location one and then when this variable gets created it has memory dress location 2 for example and then it's used within here and then two is now deleted because you've got rid of the variable because of this function but one is still alive since in the main function when you pass by reference what you're doing is you're saying give me the memory address location of the variable inside the brackets and give it into this function rather than copying the value so if this has memory just location one and you pass it into here then it's also going to have one so what this actually means is if we put this ref keyword just before the in just like we do with the out and we can place it here as well we're now saying we want to pass this by by reference so when this 10 gets passed in here we actually have a link if you will to this gome is now linked to this gome which means if we simply do n equals 20 and run the code then we're going to see 20 the main differences between reference and using the out keyword is when you're using out within a function you actually need to make use of the value if I don't include anything within here then I'm going to get exception and it says the out parameter num must be assigned so when using the out keyword num has to be assigned when using the ref keyword you don't have to make any assignment because we're just passing a reference in with the out keyword you literally tell the function I want to Output this value but if you haven't gave it a value to Output then of course it's going to be an error so we can assign in the reference if we really want to but you don't have to and it's not required so there are the two main differences between passing by reference and passing by value and also using the out parameter passing by reference is technically quicker because of efficiency when you don't pass it by reference you pass it by value which means it'll essentially place that 10 inside these brackets instead of passing the variable in it actually just passes the value and then it makes a whole new variable down here when you pass it in by reference you're essentially actually giving it a link to this memory address location from inside this function which means that you don't actually have another local variable inside here because this one is affecting this one directly you can do this with any amount of references you want by simply just changing them and adding another one in like that for example and then we can have a string name and then we can pass our ref name inside here and inside here we can say name equals hour and this doesn't like it if it's unassigned so we just give it empty quotes or we can sign it another name it doesn't really matter it's just a demonstration and if you run that but let's just print out the name as well to the screen there we go we get Abra assigned into there and same thing with this variable is we're actually just passing in the variable as a reference rather than as a value it doesn't matter what the value is going to be CU it's just given this variable inside this function so we're actually saying name equals we'll basically just assign it back into the original variable so let's just have a look at another example so we can have some sort of like change name function and we can give it the name variable as a reference and then we can give it the new name that we're going to pass in in a second so if we make a new function static void change name you're going to need a ref string name and a string new name and we can simply say in here name equals new name perfect so let's give this a shot so if we just comment out this little section and we can say console right enter your new name then we have a string new name equals console. readline and then just up here as we've done before we could just declare the name as being Joe and then we enter the new name call this function and then after we can say your new name is and then we can pass in name perfect let's run that so at this point the name is actually Joe cuz we've made it appear and then we'll enter a new name so we can type in abber now it says your new name is abber perfect so all this function is doing I know it's pretty pointless right now cuz it's just doing one line but all it's doing is assigning the reference to the variable that we pass in so what we can do now is make sure that we can actually assign this variable in and we can also pass in a Boolean variable so what we should do now is actually make sure that we can do the assignment properly cuz you don't want to assign it if the value is empty and then return back a booing type just to indicate whether or not it's being assigned so what we can do in here is just on the change name we can wrap this around an if statement and if this returns back true then your name has been changed and if not we can say console right Line new name cannot be empty or no in order to be able to do this check as we've used before we could say if new name and then just around that we can say string do is n or empty and wrap that inside the brackets and we want to say if it's not n or empty then we want to do our assignment after we've done our assignment we can return back true inside here and then just outside we can return back false notice how in this little bit of code we actually don't have an else we don't need to write else inside here and place return false inside here because if this returns back true then it's going to execute this one line return back true and since it's a return it's going to jump to the end of the function so we don't need the else in there because the only way that this line will ever execute is if we actually had this function returning back false so if this returns back true it's going to hit this line hit the return jump to the end if this returns back false it's going to skip over the if statement and then just return back false to the user perfect so now we've got no compile errors let's give it a run so we want to change your name to nothing if we just press enter then we can see it says says new name cannot be empty or no and if we type something in then we get our name changed so just to round up this video let's talk about the main differences between the ref parameter and the out parameter when you sign in by reference you actually have to make the variable before you pass it in for example you can't just write ref string in here and that actually works whereas you can't actually do that with the end let me demonstrate so if you had the in. trass and that has an out parameter you can actually type out in index inside here you don't actually have to make the int index inside here and then specify it outside you could just initialize and declare the variable straight inside the brackets whereas because you're passing a reference with the string you actually need to make the string first and then pass it in so that's a big difference between the out and the ref when you make use of it actually inside the function if you're using a reference then you never have to assign it or at least it's not required you could have a series of if statements inside this body and then you might determine that you might not need to assign it which is exactly what we've got here the only way we assign name is if this returns back true if it doesn't return back true then we simply don't assign it and move to here this is a problem if the out variable if we change it to an out then we're going to get a compiler error because it doesn't return back a value so we'd have to write something like this at the top name equals something and then potentially sign it here and then return back false so with reference you don't have to worry about the fact that you might not assign in every single path of your code and finally the main difference is the fact that out parameters are still used by value and this is by reference reference will be slightly quicker since you'll get the memory just location being passed in instead of the values so you won't have two copies of the same variable the focus of this task is to create a function that calculates the area of a triangle so we're going to ask the user for width and height install them both create a function to calculate the area the function is going to calculate it using width times by height taking that calculation and dividing the value by two call it in the main and print out the area of the triangle to the screen so let's start with entering the width and the height so we can say enter width callon and have int width equals convert to int 32 console do read line and if you copy these down change width to height and change width here to height and just before we continue because we did copy and paste down then this is quite bad and we should use a function here so in both of the cases we're going to output something to the console and then read it in and convert it back as an integer so we it says static int because we return back an integer so we can store it we can say read int and we want a string message so we can pass in this value inside here so we take these two lines and place inside here instead of enter height we're now going to have message instead of int height we're just going to have a return value and then we're ret return in the conversion from the console read line and now we can use it inside here read in and inside inside the brackets you want to put the string output which is going to be enter height if you paste that inside here and then do the same thing for the previous section and change height to width and now get rid of these so we just have these two lines perfect so let's just print these out to the screen on separate lines just to make sure it's working see the width of 10 and height of 15 we get 10 and 15 Perfect Since that's working okay we can now create a function that can calculate the area forward so we can get static int Cal area and we can have int width and in height and then taking this formula we can simply just do return bracket width times by height / two as you can see this is literally exactly the same as what we've got here it's crucial to include the brackets because we want to do this calculation first take the value of that and divide it by two if this is too many steps you can actually break it down we can say in calculation is equal to to the width times by the height and then we can simply return calculation / two back to the function it's slightly grayed out because we haven't use it but that's not a problem we're going to use it now I personally just to prefer is to keep that inside here and just have the brackets since a bit more obvious to me what's going on but it's up to you as the programmer either way it makes no difference it's just more for the programmer's convenience so now we need to call the function above so we can say in result equals calc area and then pass in the width and pass in the height and then we can have console right line that just says the area is and then result and then let's run it so you have 10 and 15 and there we go we get the area is 75 perfect if you didn't want to call the function inside here and St it inside a variable you could just output this straight to the screen by placing the function calls straight in the cly braces and if you run that again just to make sure 105 and we get 75 again perfect so just a quick little recap we have the console right plus the convert inside this function which will let us return is back an integer and we can pass in the message straight in the variable to make this a little bit quicker and a bit easier you can actually just change this one word inside here so you could actually say enter message call on space and then just inside here you can say height and just inside this one you can say width just to reduce on code because in this specific case the only thing that changes between them two string variables was the fact that one was width and one was height there we go you can see it's exactly the same now so after we read in these two variables we pass it into the function and all the function will do is take width and height times them both together take that value and divide it by two and return it back to the user and then we can call it straight in here the area is calc area and pass in width and height in this task we're going to create a function that will return us back with the sum of numbers inside an integer array so first step is to create an initialize an array of numbers create the function with the int return type and it also takes a int array as a parameter the function should return a total of all the numbers inside the interray call in the main output the total and just for extra bonus points inside the function instead of using a for Loop immediately you can check if the array length is greater than zero and then return minus one if it's empty and then check that inside the main and then output a specific message and also see if you can think of any other implementations you can use instead of having to do return minus one how else can you make this function whether that means you have to change the parameters of return type or anything like that just have a think about the situation and see what other options you can make of course the output at the end is still going to be the same but it's the way you do it and the problem solving skills that I'm trying to get you to get used to let's get started so let's create initialize an array of numbers so you have int numbers equals new int and let's just allocate them manually 1 2 3 4 5 and add a semicolon there we go now let's create the function sum of numbers and we want it to return integer back with the total then we want to take an in Array called numbers and then inside here we need to actually return back an INT so we can create an in total make that equal to zero and at the end we can return total and then during the middle we're going to have to write our for Loop so we can go through the integer array and count through everything so we can use a for each V item inside our numbers and just inside here we can say total plus equals item perfect so if we can call in here we can have a console right line and we can just say sum of numbers and pass our numbers array in the parameters so we're just going to Output it to the screen just for the time being so sum of values from zero all the way till 5 is 15 perfect so now that we've done that we've created a function that Returns the total numbers call it in the main output the total so we can just say the total the total is and then wrap this around in the C brace there we go the total is 15 now with the extra points we can check the ray length and return minus one if if the array is empty so let's see what we can do in here before we even end up going inside anything to do with the total we can wrap this around in if statement that says if the numbers do length is greater than zero then we can proceed with this little section so if we highlight all of this hold alt and press upar key then because it's one back just press tab ones and just press the delete key here and let's get rid of the empty Line This is going to return us back with an error because not all code path return a value if this returns back true then we'll eventually hit a return but if this return Z false then we not do anything inside here so let's have a look at our requirements return minus one if the array is empty this dictates whether the rray is empty so if this returns back false then it's going to come into here and we can say return minus one so we've got this function call in here we don't want to print the total right now because we want to make sure that this total is actually greater than zero because we don't want to make a sum of the numbers if the array is empty so if you run this right now going to get the total is 15 and if we get rid of all these variables and just have the length of five but not give it any value so all the values are going to be zero then if we still run that then the total is going to be zero but that's still an acceptable value because that's actually got values inside but if you said the array length is zero then the total is minus one of course we don't want the user to see minus one so we want to bring this back and instead of calling the function immediately down here let's call it here we can say int result is equal to this and then we can say if the result is greater than minus one then we can output the total and again press into this line hold alt and press Arrow key and then we can place the result inside here and the L's to this will be canot add up and empty aray there we go so now if you run it we should still see 15 but if we get rid of this and put it back to zero there we go we cannot add an empty array so we bring that back perfect so now if we check this we've got check in the main output the message and then now we've got this little solution do we need to return minus one how else can we make this so right now we're going to have to return back minus one cuz that's the only way that we can tell the user whether or not it's been successful if the ray is empty we return minus one and if the ray is not empty then we return something greater than minus one which will be something above zero or Zer itself but as long as it's greater than minus one that's how we know it's complete but we don't actually want to do this we want to be ideally returning back a Boolean so let's duplicate this function and show you both implementations let's change this into a and then because we're still going to need to reference the total we're going to have an out in total so we need to change up a few things inside here instead of this return minus one we can do return false to indicate that it hasn't been successful instead of returning back total we can actually just return back true now we haven't done everything yet we don't need to redeclare in total inside because we already declared it inside here so we could just initialize total to equal to zero but the problem here is if we make total equal to zero just within this path then it's still going to complain that total must be assigned so we can take this and just assign it right at the start of the function just like that there we go so we make total equal to zero that gets rid of the compil errors and gives it a value the reason why we have to give it a value is because this out in parameter doesn't like it if you don't assign the value that is a requirement for using the out parameter so make total equal to zero check the numbers length If This Were to return back false then we return false to indicate that we can't do anything if this returns back true it will go through and count all of the items place inside total and then return back true so let's have a look and see what else we can write this little section of code so instead of having to call inside here and use it within there then we can actually do this another way the reason why we actually calling this straight inside here is because we can't place this straight into here since it returns returns us back with an integer and now that is actually fine if that returns back with integer cuz as you can see there's no problems here the issue arises is when we have our result variable we can use it inside the bracket and down here there's no point in calling this twice to get the same value although this would still technically work but this is not really efficient since you calling the function twice it's best to call it once store the value and then make use of it twice when we use our out parameter you'll see that this gets a bit easier so straight inside the if statement we can say sum of numbers and then we can pass in our numbers and then space out into total and what that'll do now is because this returns us back with the bull we don't need any additional conditions like we have one here cuz this will turn us back with a true or false true if it succeeds false if it doesn't so we don't need to say if it's greater than minus one because we don't actually care about the value of the total right now we just care if this returns back with true or false so inside here we can take this same output message and instead of having result here we can have total and then we can take this exact L statement and place it here and let's see what happens now the total is 15 and the total is 15 so they're both return back the same values let's add something else on here just to make sure it works there we go so you can see that both these Solutions look very identical but one is considerably different we have to make a variable outside use inside here and use inside here whereas in this function we can actually just call the function straight inside that will process our new out into total and then we can simply use total inside here and we don't have to require another additional variable just outside here as this one will and you can see that the functions is a little bit better because we're returning true and returning false to indicate whether or not it's been successful whereas in this solution we have to return back an arbitrary value and then check that in the console the reason with returning minus one is kind of a problem is what if these numbers are actually all negative then this value is going to be very bad this can only read work if all of these values are positive if you had negatives for all of these and we tried running the code there you go this is a major issue cannot add up an empty array well it's not the fact that it is empty it's the fact that these values are smaller than minus one so you don't actually want to be going with something like this approach where you're comparing the value because you don't know what numbers are going to be typed into here if the user were type in positive or negative you want to provide a solution just like this one that works for either positive or negative you don't want to restrict that by checking if it's greater than minus one will only works if all of these are positive values all this is an index for the array since arrays start at zero and go upwards you can't have a negative -1 array position but in terms of numbers that are randomly typed inside of a ray you should always be wary of using this option because if some of them are negative then this could return back false so let's just have a quick recap so we have an integer array we have our values initialized down here and then the first solution we call the function pass in the numbers array get our result back check if it's greater than minus one then that means it's been successful so we print it out and else we tell it it's an empty array now second option we actually call the function because it returns back a booly in this case so we can place it straight inside the if statement and then we can pass in the numbers array and then we have it out in total which will give us the total and in this case we don't need to check the value because this returns us back with the true or false and in this case true determines whether it's been successful and false it doesn't if it returns back true then it has some values inside the numbers array that we can actually add up and if it returns back false then that means the array is empty so let's have a look at the implementations so without the out parameters this is the first solution up here we get the numbers length check if it's greater than zero if it's not we return minus one make a new variable called total make equal to zero and we run a for each Loop of our item inside the numbers and we just say total plus equals item add them all up in the for Loop and simply return the total and then in the out solution we have a total equals zero which just initializes this variable otherwise we'll get a compile error then we can say if the numbers is greater than zero then we can say if numbers. length is greater than zero then we can do the for Loop and return back true and if this turn back false then we can say false inside here and then when we use it straight in the brackets we have access to it straight away since it uses a Boolean variable and then our value will be placed inside our out into total parameter which is used down here for the output to the screen and again if this returns back false then it will say cannot add up an empty array and then we hit the console read line and way at the end there we go that covers everything inside here exceptions are used to prevent your code from crashing and then the program closes down let's have a look at a very very common example let's have a console right and we can say enter a number and then we can use int Norm equals convert to int 32 and then we can have a console. readline inside here and let's just print out number to the screen now if we assume everything goes well and we actually enter an integer like 15 and we press enter then we simply get 15 returned and as we saw in the past when we covered the trass function if you enter anything else that's not exactly a number then you get again exception exception unhandled unhandled means that we haven't wrote anything specific that will handle this exception so it's causing the program to close it's a system. format exception it says the input string was not in a correct format so this is a format exception because we've entered in a very weird set of characters that can't be converted over to an integer so now our program is forced to crash and now rest of our code is going to be deleted now because it won't be able to run so if you had any important data that was stored just before this point then it is now lost this is very crucial because if you have a system that rides to a database or it stores some very important information that someone's typed in you want to handle the exceptions so if something were to arise it doesn't actually close the program down and they lose all of their data I'm sure you've had it in the past where you've tried to do something and the program comes up in Windows and it says this program had to stop responding when that normally comes up it means that Something's Happened that's so fatal that the program cannot continue it has to crash down and in most cases this is what's called an exception so if we run this code again let's have a look and see what else we can do to make this code break so of course as you heard before a num integer can only survive up to about 2 billion numbers so if we enter a number bigger than that let's see what happens then we get an overflow exception value is either too large or too small for an in32 of course this number is very big and only a long would handle something like this an integer definitely won't so these are the kind of exceptions where you'd have to handle it yourself manually otherwise your program is going to crash coming up next we're going to go through the ways that we can handle these and make sure programs don't come to a halt exactly like these examples I want to explore a technique called TR catch this is very similar to when we use the int. trass what this essentially does is it tries to do something and it lets you know if something went wrong this is exactly the same when we're dealing with exceptions except when we're doing a try catch what the catch means is catching the exceptions that happen and therefore it is now a handled exception instead of unhandled exception so before we try and fix how this works let's just explore the syntax so we can type in try followed by curly brace and just after this curly brace we can say catch then we're going to put something inside the brackets and then we have an opens brackets if you wanted a quick shortcut to this just like we've done the for Loop and we double tap tab we can actually delete this so you can type in try and press tab twice and then you get try the Open brackets you get the exception and then we get throw so let's get rid of this and what we can do right now is we can actually place the Corde that we want inside here inside this Tri bit because we're telling the compiler that we want to try to do the things inside here and then we want to catch these things so inside these brackets what you want to actually do is decide what thing that you want to catch if you type in exception this will catch every single exception now the problem with that is you'll actually face some difficulties when you're trying to Output very very specific messages so as we've said before when you type in a value too large you get an overflow exception but when you type a value that can't be converted like a square bracket then you get an input format exception so first what you actually want to do is run this code outside the try and let's run it now and let's get them bad values so we had the square brackets and we can get this and let's copy it down and place inside a comment just like this and then let's rerun it and if you type a number too big take this stop the program and put it inside here so now that you know what the exceptions are called we can actually write write these inside the code so we have a form exception and an overflow exception but before we get into these specific exceptions let's just catch everything this is just a catch all and then see how this works so as we've put it back inside here let's see what actually happens so we can just put a console right on here and say something has went wrong the reason why something has went wrong is because this is a catch all any exception appears during this code it will always come into here regardless of what the exception is whether it's a format or an overflow it doesn't matter it will always come into here so it's going to be something because this is not specific at all so let's run the code enter very big number something has went wrong but if you notice how the program doesn't actually clash it's still very much alive and we can test this by putting a simple message here at the end that says goodbye and we run it again enter a big number and there you go we get the message as goodbye so it successfully skipped over this section without actually causing an exception that breaks the program so even though we've entered something very fatle because we've handled it then there's no problems so if we now type the other one where we have the square brackets then you'll see we'll also get something has went wrong so if you wanted to catch a very specific exception what we can do is say catch open the brackets and we can say format exception just like it says above here and then place the curry braces and what you can do now is you can actually chain these and these go from top to bottom when an exception occurs up here it will match this one if it doesn't match it will match this one and you want to put the catch all right at the end so if it doesn't match any of the ones above it it will always match the last one so you can have a generic message inside here but you can have a very specific message inside here because it's a format exception you can say please only enter numbers so now if we run the code and if we type in square brackets it'll say please only enter numbers there we go so this is a very specific example and if we copy and paste this down again and then we can say overl exception and we can say please enter a number less than 2 billion if you enter a very big number again please enter a number that's less than 2 billion perfect so this will get checked like if statements it will start on the first one and go down the list imagine this is a if and then we have an lse if and then lse if as well if you place this one right at the start then you're actually going to get compile errors and you can't actually have the catch all right at the start so even if you wanted to the compiler literally doesn't let you and anyway you don't really want to be doing that because then you'll be ruling out these two and it's kind of pointless writing this code if it's never going to get used anyway so now when we run the Corde you can see even if we type in a bad value our program will still run and everything works okay so now what we can do is actually make this into a real life situation so if we actually type in 10.2 that it says please only enter numbers then we're going to have an issue here because if we try and print the value down here then it's going to cause a problem let's try and print out num and you can see that num does not exist now we have an issue of scope int is only declared within here and here so if you wanted to print out the value of gome we'd have to print it out up here so now let's run it again and if we enter 20 20 comes up if we've entered 15.5 then actually skips over this console right line because the exception occurs right here and then it'll jump into one of these paths so in order to store the value of num you can either move num outside here and make it equal to zero and then assign num inside here and then you can take this console right line and actually put it right after the triy pass but I don't really suggest this option so if you said 15.5 then you're just going to get zero returned but we don't really care about the zero because we're not going to get the value converted so why do we need to print the zero and the answer is we don't so what we should do is keep it all inside here again and then what we should do instead is wrap this around in a while loop so this will try to do the code this section will catch them all and then we simply have a good buy at the end but let's just make sure that this actually runs because if we type in 15.5 then the user still hasn't entered the number but our program is closed so we want to loop around until the user has success successfully enter a correct number so we can say bull looping equals true and we can have while the chord is looping then we can have the curly braces let's place our entire Tri cut inside here if we highlight it all hold alt and press the op power key and then tab it once and then get rid of this empty line so now we'll keep looping around here until this is going to be a different value so because the while loop will only keep looping until this is true and the moment when it's false is when it will cancel while loop so as I said before it when we run this code and then just at this specific line if the exception occurs it will actually skip this line and jumped below here so if it ski this line then what we can actually do is we know if it reaches this line then the conversion is been successful so we can print out to the screen and we can say looping equals false and we don't need to place looping is equal to True inside all of these three paths because if we don't assign it to true then it's still going to be the value false no matter how many times you loop around so let's try and run that now enter a number 15.5 enter a number 15 and we can keep doing this forever as it's a while loop and as soon as we enter a valid character 20 and now it says goodbye because we hit the end of the program so that's it for this video but let's just have a little recap so we've determined when we run our code just these two lines that in both situations we can have a format exception and it all overflow exception we can use these to catch them specific exceptions and then have a catch all at the end the reason why you want to catch multiple is you can have a very specific message overflow dictates we have a number that's too big or too small to fit inside of an integer it can be less than -2 billion or can be greater than 2 billion and that's how you get the Overflow exception we get him a format exception if you entered something that's literally not a number or something that has decimal places and then I'll catch all can be if anything else goes wrong we can output a generic message but in 99% of the cases you'll either enter a number too big or too small or it's in the wrong format and this exception is just so it catches everything else should anything else happen so at this point even though our program doesn't actually close and there's no exceptions the user hasn't had a chance to enter the number again so we use this inside a while loop and we can say while looping is true when we hit a conversion that's successful we say looping is equal to false and once it hits this line the Y Loop will then exit and then we'll get our good goodbye message and we wrap the entire TR catch inside the W Loop just so this keeps on looping until the user has typed in a successful value as demonstrated above we can type all this and 15.2 15 Point 15 and then finally says 15 and then goodbye so I want to explore different ways you can output messages inside this catch block when you have a catch exception this is actually a parameter that we're passing in this parameter can actually have a variable as well normally when you specify parameters in a function form you say int and then something whereas right now we're kind of defining the data type which is our exception in the same case as in in here but we're actually not giving it a name so it looks something like this of course when we do this inside a function we're going to get a syntax error but for a catch we're not going to get any errors at all and the reason is because we can catch without having to use a local variable so we actually add a local variable make you call it e for exception then we actually have lots of options inside here Type e then we have lots of data and the stack Trace is very helpful when you debuging but we'll cover that at a later date the thing I want to focus on right now is the message so we can use this and print out to the screen so we can say error callon and then type in E message and let's run that now if you enter something invalid input string was not in a correct format if you enter big number then value is either too large or too small for an in32 as you can see these error messages are pretty descriptive and normal users should be able to read this and understand it of course if you want this error message to be more specific then you can add some more catches inside here and we can have format exception this will be if you type in something other than number but if you do exactly the same thing in here then it's kind of redundant because you're just outputting exactly the same value if we try to put the square brackets again then we're going to get this this string which is actually outputed from this line but even if we include the catch all exception you get exactly the same error message outputed from here the moral of the story is you should always have a catch all right at the end of your chain but if the only thing you're going to do inside here is simply output this message to the screen then you don't need any multiple catches what you should do is catch multiple exceptions that you know are going to get fired in your code and then you want to handle them and then have a catch all at the bottom that will display the message generically instead of displaying the message right here you can actually have a more specific message like we covered in the last video so this could be please only enter numbers and we don't actually need the message in this case because we know what exception we're going to catch because we've specified format exception another little tip if you hover over the function call it says here format exception and overfall exception which is the two that we handled in the previous video this is very easy and understandable if you can just read the values from here into see what exceptions can get raised and the same thing here you get an IO exception for the console right line the console right can also give back an IO exception as well generally speaking these console functions almost never return back exceptions I don't think I've ever hit a situation where this exception has been returned unless you do something ridiculous and maybe you type in way too many values that the console right line can handle let's try an example and we can do something like this if you enter a very big number that can't be specified inside an integer then console right line has so many overloads that it actually processes it as a long right now so you almost can't break this unless something fundamental to your computer actually happens so you have exception e and with exception e you can actually take this local variable and print out the message this is the preferred pattern because instead of outputting here something went wrong just very generically you can actually give them the error message that comes back from the exception the reason why this is helpful is because if it doesn't hit any of these exceptions and it just happens to fall into the catch all at least the user has an idea of what the error message is going to be the preferred option is to try get to a point where you never have to reach the catch all and try chain as many catches as you can in order to handle as many exceptions based on the code that you're writing which can be found if you hover over the function and read the exceptions once you've covered as many options as you can throughout the catches then you almost never have to worry about the code entering this section because we've covered both the exceptions in format and overflow and we can do overflow right now please enter a value under 2 billion then that means we've actually covered all of the catches that are to do with converting in integer 32 covered format and covered overflow so when we run this code the only two things that can possibly go wrong are these two functions the format exception overflow exception and we won't ever hit the catch all in this case but if anything goes wrong at least we have a belt and Brace option to catch it and we can tell the user what happened and because it's e. message then the value is going to be quite descriptive so the user can read it without any problems so in this task we want to be able to convert a string to an in successfully without any errors occurring and without any exceptions that could break our code so in steps we want to create an INT and try and convert any string from the console to an integer notice the error that appears when you try to do that write a try catch Handler around it to successfully operate that and output the message to the screen and you won't need to change the console out print and convert in 32 to be able to make this work so you don't want to change the current code you just want to add the Trion Handler around it so why is this a bad situation how can we know if it's been converted this is just a question that you should keep at the back of your head and we'll answer this shortly and then finally we want to create a custom trip pass function find the real trip pass function and copy the return Titan parameters and see if you can mimic Its Behavior read the tool tip it gives you to give you ideas on what to do so let's take these in steps first first we can have a console right and say enter a number and then int num equals convert to in 32 and then we need a console read line and then if you run the code if we try and just convert some square brackets then we get a format exception so that's the exception that we're going to be handling right now so we can take this code and we can wrap it around in a try use alt and up Arrow key and then just have to do a c and then we want to do a format exception and then space e to give it a variable and then we do e. message out to the screen and now let's run the code square brackets input string was not in a correct format so we get our message and our exception has been successfully handled and our program hasn't crutched but the problem is is has got to this console read line and the user hasn't had a chance to actually enter a number so what we can do in here to ensure the user always has access to writing a number is we can say something like this bu success equals false and then just after here we can say success equals the true and just down here we can say console right line success question mark yay and then call on or no so if it convert it 15 we should get a yay and if we convert it and it fails then we should get an o no along with the message of course what you can also do is wrap this entire section inside a y Loop what we've already covered that inside the tutorial and that means we keep repeating this until this is set to true and therefore exit the while loop and then will the users finally typed in a number so let's go back so we've noticed an error and we've wrot a tri catch handle around it now we want to catch the error and output the error message with through done and then we haven't changed the current code which was these two lines we've added a the booing and set it to True here just so we can have a bit of an output message before so why is this a bad situation how can we know if it's being converted so this code is a bad situation because we just have these two lines outputed and then now that you've added our booing to tell the user whether it's been successful or not is actually making it a bit more meaningful the problem is even if we print or no then the user doesn't really have a chance to enter it again so like I said before you could loop around and use a while loop to make sure that this situation can go from something that gets handled into a situation where the user can actually type it in there's no point hand on exception and realizing there's error if you don't give the user a chance to enter another value if they enter out 15 Follow by full stop when they only meant to type 15 then you need to give them another chance to type in that 15 value otherwise the program is simply just going to end and nothing's going to happen for example 15 DOT it says oh no or you can have another message that says something went wrong or you can have more specific message about the conversion and then once you press enter the program simply closes this is not an interaction that you want you want the user to be able to reselect another value so that's why it's a bad situation because you know it's been converted or not use now Bill success but the problem is we don't have any sort of looping so let's have a look so now let's comment out this and let's see how we can make our custom trip pass so we type in in. trass you can see they have a Bo inpass string s and out in result so let's try and copy that and make our own custom function so we say static Bull and then it's trass and then we have a string input and out end result perfect so now we can get rid of this line just so we use it for reference and let's use it straight in here and then we can write the implementation in a second so we can say if try pass the thing that we want to pass is actually a console read line and then we just say out into result and the console read line is going to be answered to this question which is enter a number we place it straight inside here and then we say out in result so if this has been successful we can print out yay again and else if it's not successful we can print out or not of course you can do other things inside here or you can even print out the value straight from here so we can say yay plus a space and then result just so we can get that back to the user and then oh know if something goes wrong of course this is just so we can test things and see how they work so this trass function it will take in a string input and it will try and give us back the result so in order to be able to make this successful function what we need to do is essentially do the conversion ourself which will be this convert in 32 so first we need to assign this out int so we can say result equals minus1 so now that we've used that we actually need to have return type as well but let's worry about that in a second so essentially what we actually want to do is say that the result is equal to convert to in32 and then we want to convert the input store it inside the result and if this goes successful then we want to return true and if it doesn't go successful then we want to return false but of course we need to be able to do these things separately so like we said with the try you only wrap around the section of which is going to be problematic so in this case as we've done here we've wrapped the convert in 32 inside the try so we're going to need to do that down here as well so we can open the try right here and place these two lines inside and then have a catch have a little think about what sort of catch do we need the whole point in this function is to Simply convert value and return back whether it's been successful or not there is no messages here we just need has it been successful yes or no and because we only need to know if it's a yes or a no then we can just have a generic exception and we don't need the E variable because we're not going to access the message we're going to keep it as an exception and instead of returning false down here we actually want to do this straight inside the catch so now the code reads like this we set the result to minus one and the reason why we do that is because if we don't then we're going to get a compiler error and it says that not all paths were going to assign result alternatively we can also assign result straight inside here just so we have an assignment in both paths or you could just leave it outside at the top so we assign result to minus one and then we place our problematic code straight inside here we try and convert the result and if this line returns back successful then it's going to execute the second line and return back true if this line returns back an exception it's going to miss this line completely and jump straight into the exception and then return us back with false so let's actually try this and see what happens 15 DOT or no and then 15 yay 15 so the reason why we don't care about the exception in here we can add in different values as we've used before with format exception overflow exception but as we saw with triy pass it simply just returns us back with the bull the bull simply tells us if it's been successful or not so we could stack these multiple times we can say catch and then we have the format exception and then we can place a return false in there and then we have another catch for the Overflow exception and we can place another return false in there but as you can see we're just returning false inside here so now that we've changed these it's kind of pointless each of them return back false and because we're not doing anything very specific we don't actually need to change them all together we don't care about the message we don't care the exception we only care about the fact that something has went wrong and if something has went wrong then we turn back false if everything goes okay then we return back true and that's all this Tri pass function is going to need to do it simply converts it or it doesn't convert it using an input and outputting a result so if you run it weet type in a real number we get a number back and then 15 DOT zero then we get all no because it can't come it there we go we've met all our requirements for this program let's have a look at how we can do debugging using visual studio to step through our code manually so this is the example I used last time int age equal 35 and ideally in this case you'd want something like 30 plus to be printed instead of 18 plus even though 18 plus is still technically true we'd still like 30 to be printed in this case because this says if it's over 18 do 18 if it's over 30 do 30 plus so in order to start the debugging process you shouldn't run the code first if you run the code first it's going to execute so fast that you won't get a chance to actually put any code in and try and debug it there we go we've already hit the console read line and it's executed for a split second so the best thing to do just to the left of the line numbers you want to press in the Gap and that will create a red dot and it'll tell you that this is a debugging Red Dot just in this little tool tip debugging do program. Min debuging program main so it tells us we're in the program class and we're going inside the main you can also address the debug menu up here and it says we can have a toggle break point we can add new one we can delete them all or we can actually disable deleting them will just simply get rid of them as you can see here if I set a couple more and press disable then it's going to hide them so whenever we run our code it doesn't actually apply the debugging but it doesn't delete them and then we can enable them and then we can also delete them all and it gives you a little prompt because if you do doing this inside a big project and you just spent a lot of time going through and debugging certain functions then you don't want to be able to delete them all without any confirmation so let's delete them all and put it back on line 13 which is our int Edge so let's run the code and see what happens so as you can see it minimizes our console for us and nothing's actually been printed yet because we're only up to this line and then we can use these buttons up here step into goes inside a function step over goes over the line so it will go from this line to this line step out is used after you've stepped in if you stepped into a function and then you don't want to see the rest of the function executing you can step out to jump back out of it which I'll demonstrate later on in this video so now that we've hit this line you can actually see what's going on so we have in age equals z because when this line is highlighted it means this line hasn't executed just yet so we can press this or we can press F10 on our keyboard if I press F10 you can now see in age has the value of 35 and what you can actually do is double click on it and just change the value to 30 for example now if you highlight you can see the value is 30 so you need to double click change the value to something and then simply press enter if you change the value but leave the box like this then it won't change the value so you have to remember to press enter so now I've made the age 40 but let's just change it back to 35 to keep it the same and then now what we can do we can explore what's going on here if age is greater than 18 then we're going to check if this condition is true or false so in order to check if this returns back true or false you can actually hover over the operator and it says here AG is greater than 18 is equal to true and if we hover over this one it says age is greater than 30 is equal to True notice what we actually did there we essentially ran this condition through the debugger without actually reaching this line we're only up to line 15 as of right now but we've managed to execute this and give us back a function so as you can see age greater than 30 is true and age greater than 18 is true and because this is L if chain it only cares about the first one that turns back true and because this one has turned back true then if you press F10 again you'll see that now it's went inside this curly brace which will print out the console right line if I press F10 again you can see we're now waiting on here if I use alt tab I can get back to the console you see that 18 plus has now been printed now that we're waiting here we actually press F10 one more time and then it jump straight to this read line of course because this is L if chain as soon as one of these become true and it jumps over the lse if because of course this is a chain the first one it hits that's true it skips over the rest if we didn't want this to be a chain then we could keep them as both independent if statements if age is greater than 18 and if age is greater than 30 and don't use the lse keyword but in this case because you do want to Output a different message for every single age range you do want to place the L's word in there and now that we've hit this line we can press F10 and then now we jump back in the console and now we're wear in right here and just a little tip when it comes to debugging if at any point you just want to exit the debugging you can either press continue or just press F5 and the program will run for example if we investigate this variable and we can see the value is 35 and then now we're happy with the rest of the code we can just press F5 and our code will run as normal we'll get the out print and we'll get a read line waiting here so we know our problem here is both conditions return back true so just like in the last video we actually changed this condition so to make sure that it only goes between this range but let's not repeat ourselves let's have a look at a different example so we can have string name equals Abu and then int age and then age equal 23 which I'll demonstrate why I've done it like this in a second and then let's have a function just so I can show you how to step in so we can have a static string print details string name in Edge and here actually we want to just return back a void because we just want to print out to the screen and we can say name space edge and maybe just put a dash between them and let's run that code now we can see ABA -23 of course making that function wasn't the point I actually want to show you what's going on so if we just print this a couple of times just so we can show you the step out and step in so you run the code now we can see our string name if we go over that you can see it's called abber and then now that it's stepped over this line cuz there's nothing really to execute here it's just creating back a variable so you can see that age is zero cuz that's the default value for an integ and when we skip over that now it's got the value of 23 so one line creates the integer with the default value equal to zero and then the next line will make it equal to 23 and then we're passing on the variables here and if you wanted to investigate it you could simply just hover over them like this so you can see what the values contain and then now that we've hit this function if we press F10 then it's just going to skip over it but what we actually want to do is be able to go inside the function so this is where our step in goes step over doesn't doesn't care if it's a function or a normal line it'll just step over it regardless so we want to in here we want to use step into or we can press f11 once you press for f11 you can see that now it's jumped from print details up here to print details down here and then now look if I step through it's going to actually execute these one by one so right now it hasn't executed anything so I step over this once using F10 you'll see it now appears and then the same thing with this one and this one and now that I've executed three we should see three in the console perfect so now what I want to demonstrate is let's say we're happy with the rest of this function and then now we want to just step out so I press this button and you can see it jumps back up to print details f11 to go in and then shift f11 to go out so now that we're back in here the only thing we can do really from this point is either press F5 to stop debugging or press F10 to jump to this line and at this point we've already hit the last line now code so we don't really need to use F10 anymore cuz with nothing to step over so we can just press F5 let our program finish and there we go so let's have a look at another example can have a string message equals read from console then we can pass this in enter anything and then we can have a console right line and we can just print the message and then let's create this function so because it's a return value and store inside a string we're going to need a static string read from console and then this is one string parameter so we have a string message and then we can just do a console right and then print the message to the screen and then we just want to return the console. readline there we go and again let's put a breakpoint here and we can remove this one so it doesn't always have to be the first line if we're perfectly happy with this amount of code then we can simply take that off and it will stop when it gets after this line now if you look at the console you'll see all of this is executed that function is executed four times to print the name name and age of the screen and now we're waiting here so we have our read from console and now we can step into using f11 and you can see that if you hover over string message has enter anything which is our parameter that we specified up here and then there you go and then that will print into the screen so you tap back in you'll see it says enter anything and then just at the read line we need to actually enter it now something and then press enter and then just right here it's going to return it back so if we use F10 it jumps back in here and then actually we need to execute this line so F10 again and then if you hover over a message you see it says something which is exactly what we typed in the console here and then we just print it back to the screen there you go and now we just at the console read line and we can press F5 to finish up there we go so debugging is mainly used by pressing this button on the side so debugging is used by pressing on the empty Gap just to the left of the line number and it will create a red dot once you create a red dot it'll highlight this for you once you've clicked done it it should show up a red dot you can also disable or delete all the break points from the debug window at the top of the screen when you run the code it will stop here and then you can either use F9 as a shortcut as well click into the line that you want to debug and press F9 please note there is specific cases where if you try and press this one right here it's not going to let you if the line doesn't really do anything for example this is creating an integer there's no real action that's happening here that you should or want to debug this is an assignment this is an assignment this is a function call and so on and so forth and this is also a function call when it comes to just declaring variables then a compiler does not let you put in a breakpoint because there's nothing really to investigate when you're just creating a variable so don't get thrown off or think something's wrong if you click on the empty line and nothing appears so that's it for debugging but let's just have a little recap we can use F10 to step over f11 to step into functions shift f11 to step out or you can use the buttons that appear at the top of the screen when you run the code just right here hover over variables and you get their values as I showed you in the if statements if you hover over the operator inside the if statement it will actually tell you what the condition is and whether it's true or false so me say if1 equals equals to 1 and let's just print out true to the screen just so I can demonstrate this if a hover r that equals equals it says 1 equals equals 1 is true so that's how you check if a condition is going to be true or false when you're debugging you can check the parameter values by simply hovering over it and the tool tip should include the value just like so and if you wanted to step into this function you can use step into and then use step over which is F10 just here and then you can actually investigate these values as well or you can look at the parameters and once you're done with the function you can do shift f11 or you can use step out and then you can skip over this and the same thing with this you can have a look at the string variable once it gets returned something in here and now it says something in here and string message and then we can print out to the screen Etc so you can have a little bit of Freedom with what you can do in terms of debugging play around to debuging in the past exercises that we've made together and then what you can actually do is gain experience in debugging so it comes to more complicated projects you can also apply that learning there and make sure that your code is error free so we covered how to debug by pressing the white space just to the left of the line number if we run the code the program will stop where our breakpoint is and it won't execute the line that we're up to we have to step over it so we've actually use this before to analyze our functions and see what values are inside things so we have these extra windows called the local and the auto so let's take a look at them and see what they're about so again if you don't have this layout you can use window reset layout and it should be in the left panel not the right one this time so we've got watch which we'll explore later and we're going to have locals and Autos so the autos because we're up to the age then it shows us the age has value zero and then that prevents us from hovering over it and if we step over it you'll see that now it's got age 23 and now name has appeared the auto tab will try and figure out what functions and what parameters you need to be displayed down here based on the section of cord that you up to so my guess is because we're up to this function and it takes in a name and age then we're getting name and age appearing before when we were on this line it was only showing back the age and because that section only used the age we only got age here but if you press locals you can see all the variables that are local to this main function are actually showing up we have a parameter called ARs and technically this is a parameter and it's a string a ray type but it's currently unused but it's still a parameter so you can see it down here and then in order we have have the name variable down here then we've got the age and then we've got the message which is currently said to know because we haven't created this in memory yet but as you can see this changes depending on the scope of our variables so now that we're about to hit this function let's use the step into and you'll see that the locals have now changed we've got rid of name age argument and string message and it's replaced with name and age because remember what I saying about the scope of the variables parameters inside a function are always going to be local to that function around the curly braces that they're surrounded by name and age is only within here so when it's trying to shows the local variables it's only local to what's inside these curly braces which in this case is name and ede so now if we step over this and then if we step into this read from console you'll see that just before we step into this function that these have all came back cuz again the scope has changed back to this function which is our main function which has all these variables inside so our read from console will only have our Str message so hopefully when we press f11 or press the step into button at the top we should only see the message variable inside here there we go we get enter anything cuz that's what was passed in over here and then as soon as we return back to that let we type something in and then we get all of the values again and you can see that system. console. reine had returned hello which is this line and then if we press F10 again you'll see that even though we've got it back here our message is about to be assigned once we step over this there you go it says hello and as you can see this changes in real time so as soon as we step over lines hello got placed straight into there this helps us tremendously because we don't have to keep hovering over variables like this to keep checking over their values you can simply use this menu and it will always update because whenever you change Scopes between functions that will automatically update as you just saw in them examples there we go and then when the program ends obviously this window is going to close down so that's a very help helpful method have being able to debug without having to hover over anything in the next video we're going to cover how to watch variables and this can be very handy when you're looking for specific errors another really good debuging technique is the watch window let's press a break point just of left of line 13 and let's run the code and let's see what this is about so we covered that we have the locals window and we have the auto window that will automatically give us the variabl that we're currently in the scope of but let's forget about that right now let's have a look at the watch window it says here add an item to watch so there's a couple ways that we can do this you can actually double click on a variable and right click or you can just highlight it like this and then right click and it says here add watch and you can press it it says name value null because we haven't created it yet so the default value is null as of right now cuz it's not actually assigned anything so you press F10 and step over it you'll see that immediately changes to abber without was having to do anything except simply press F10 which is the shortcut for our step over button right at the top of the screen this prevents us from having to hold over the variables to get the little tool tip so we can see the value the power of this is we can watch variables and we don't have to worry about showing in the locals or the auto because it's always there and if you have lots of variables like this then you're only concerned about the one that you're watching locals and aluto will always change depending on the scope that you currently at whereas watch will only do what you want it to do so because we don't put age inside there then it's simply won't come up just because it likes it if we check the locals we have agent there and the Autos we have agent there as well but we don't have it in the watch so what else you could do is actually just type straight into here age 23 if you really wanted to you can actually also type in conditions age equals equals 23 it returns back true so if you had an if statement that you wanted to track then you could do that as well so let's have a look so it a statement that said if age is greater than than 18 then we can just print out 18 plus to the screen so let's run the code now and see what happens so as you know we have this condition right here so if you actually highlight this and drag and drop it you can see that the cursor changes and you can drop it inside here let's click on the AG equals equal 23 and click delete so of course we can't really render this function right now because we haven't even created the integer variable so let's run over the integer variable and as you can see here it says AG is zero which is the default value for integer and that is is indeed zero right now and then age is greater than 18 is false but as soon as I step over this line and it makes age the value of 23 you'll see that these two immediately change you know they change because the values have went red red means that the values have just changed in the last button that you pressed whether that means he stepped into over or stepped out it doesn't matter red always dictates that the value is just changed so now it's telling us that age is greater than 18 is returned back true so when I step over this line because this is returned back true I should render 18 plus let's have a look F10 F10 and there we go we've reached the middle which means that's going to get printed out now so moving on to another example we can have print details if we go into this function and let's say we only concerned about the name then we can print out the name down here but as you can see we already have it twice so that's just going to update depending on the parameter name and even if you wanted to show something like this you can drag this down here and it actually shows you the output this is very handy so you can see the output because sometimes when you have it like this it doesn't look very clear you can also hover over it right there and you can see the value placed here but again it's very handy to have it here so you don't have to keep hovering over the tool tape just to see the values and from here you can actually change the values so we can just say Harry is now the value for the name and Harry is going to be age 35 so when we press F5 and let the program run naturally you'll see that Harry is age 35 now and that's all done through the watch list down here here and it doesn't even matter because we have full control over the watch list variables and we can change their contents to see how our code acts in different situations so please use this watch list as much as you can and don't forget that once you can double click on variables and add it to the watch just from here you can also say quick watch and what that'll let you do is it'll give you the value and then if you want to add it you can press add watch here or you can just keep pressing re-evaluate once you've skipped over some lines so let's say we skipped over it now and then go back onto it and because it has a shortcut shift F9 we can just quickly press it like this and it says abber inside here and we can change the expression maybe do something like age and then click re evalue it and it changes the value to zero and then we can even change this to like 50 for example as you can see down here it's changed to 50 as well so you can drag and drop it into here or you can double click and press add watch it's up to you please make use of this watch variable and don't rely too much on the autos and the local just so you can keep your own variables inside here and you can have complicated outputs like these you can check conditions you can check console outputs as well as just checking normal variables so using the watch window you have lots of different opportunities to keep track of your code so we've got another debugging task let's try and run the code and see what happens we're going to get printed over 18 so our value is AG equals 35 and we're already getting over 18 printed to the screen so if we place a Brak line inside here and actually run the code we can see what's going on we can add them inside the watch just like this we can add in all the conditions inside just like this perfect so we can actually see here that because our age is over 35 it's saying greater than 18 is true greater than 30 is true but greater than 50 isn't true and we can easily see that except because this is an if and an else if chain as soon as the first one is true it's going to enter that one you press press F10 then we get over 18 and then as soon as it finishes that path it actually skips all the way to the end the problem with this is we only want it to print over 30 since it's over 30 so we have to introduce ranges inside here and we can say age is less than 30 and then you can have ages greater than 30 here and then you can also insert an end and say AG is less than 50 and there we go and now it says over 30 and if we change this to 55 then we should get over 50 and then finally if we change this to something like 23 then we should also get over 18 perfect so what was going on here is because we had if and else if chains then you're only going to get one of them printed and because a value over 18 satisfied both the first path and the second path then it's only going to print the first path if we actually undo our changes all the way till the start and then we actually flip the order of this if we put our this one first and delete the El's and change it to lse if inside here so now we have a new chain except the first one in the chain is actually if age is greater than 30 now if you're on the code you'll see that the first one actually says over 30 and it says over 30 and it doesn't say over 18 anymore but simply because this is the first one in the list as soon as it hits the first one as I'll demonstrate now it will go inside this bracket hit this curly brace and then jump straight to the end you should always order them from smallest to biggest because that will probably make the most logical sense when you're reviewing your code and in doing so you can actually have a more formatted code but you need to watch out that the ranges need to make sense if you have something like this then you need to restrict this one because it's going to be blocking the second one and you don't want to make these all ifs because then you get multiple outputs now we should get 18 and 30 being printed to the screen this is not something you want so make sure that you place your ranges inside here by adding an and and then placing the other end of it which will be 30 and then this one will continue from it so so just to sum up what you need to do is make sure that you use Els and make sure that you have ranges just so when one exits it's going to check the other one and the other one you don't want the first condition to beat the second one if that's for the right path age 35 goes into this path or at least we want it to but it's been restricted by the fact that age is greater than 18 when we had it like this this is restricting everything over 18 to go inside this path if this was even like 65 we should only fall into this one and we run the code then we're still going to get over 18 which is still technically true it is still over 18 but we have different outputs for this sort of age range make sure that you use lfs and you keep in an appropriate range and keep them in the order of the if statements going from lowest to highest or whatever makes sense in that situation that you're using it this is a start of objectoriented programming let's start with a concept called structures structures allow us to store different data types inside one data type so it's almost like a group of data types we can demonstrate this if you wanted to stall something like a person you would normally have something like a string name equals ABA and in age equal 23 so in here we have a string name that represents the name and in age which represents their age and you can see that because these are two different data types you can't wrap them around inside an array you can't have a string array called person and then say we want to have two different values although this will still compile we can't store both these data types inside array unless you make the ede and store it as a string which will be 23 inside the quotation marks and then you'll have to worry about converting it later on in your program so this is not really ideal so we have something called a structure so just outside here we can say struct which stands for structure and then we can have our name straight after so we can say person in the next time we just open the curly braces and let's see what we've just created so now in order to make an instance of this we can actually use that like a data type between say person person there we go so now we've created our person variable now you see we've got our own data type before we're just using string and ins and arrays and things like that but now we actually have a new person so because our person is made up of a name and an age let's place that in here string name and then inage of course you don't want to give them default values because like all variables you don't know what the value is going to be to begin with so now what we can do person Dot and we don't actually have access to using these values yet so what we're going to have to do there is a concept called access modifiers which we'll cover on later on in this course but just for now what this means is you either have private or public and they're the main two words there's other words that you can have but they're the main two for now if you have it private it means you can't access it down here through person. name and but as soon as you make this public then now it becomes accessible there we go we can make that equal to something and if we take off public then you see we don't have access to it it's inaccessible due to its protection level because the protection level is private which means that you can only access name Within These two curly braces the second you make it public it means that anyone outside of the structure EG down here can also have access to name so if we do that to our public on int age and string name then we actually can access both now we can say person. Ag and it comes up like this the purple cube is a function and the blue is Fields you you can actually filter them out by pressing them down here show only methods and show only Fields so we can do age equals 23 and I can actually just place abber inside here now that this data is essentially the same as this the benefit that we have now is when we print to the screen we can say person. name and then hyphen person. Ag and if you run that now you we Abid 23 if we actually copy and paste this lined out and just remove person dot just so we're using these two variables at the top of here and we in the code you should see exactly the same values coming up there we go but now what's really handy about this situation is we have two data types that are wrapped inside of one data type instead of having a name and age we have a person because what gets really easy now is if you wanted to add something else inside here like for example birth month which for me is five so in here you'd have to make another one birth month equals 5 and then all we have to do inside our person is just say person. birthmonth and we could just assign it right here instead of having to create a whole new variable we add it up here and then we can use it down here and then we can add that into here person. birthmonth and we can add this to this one and then get rid of birth month and as you can see it's exactly the same so we've taken these data types and placed it inside our structure so then we can just reference it by the person this becomes very very handy for this exact reason that I'm going to show show you now let's say you wanted to read this data R from the user so you have static and then you're a bit stuck on what data type you want to return if you forget about the birth month then we have a name and age as a very basic person but our return type only lets us have one type so that's going to be a problem now so you could do a string return that will give us back the name and then we can say return person and inside the brackets what you can actually do is do out in Edge so you can have two output variables an out Edge and then a return string since hiide here we could say enter your name and then string name equals console do read line if we copy and paste this down and then we can say enter your age and then we can say int age equals convert to and 32 and then put the console read line inside there there we go now that we've got that we don't actually need inage because we've already got output parameter so we just need to be Edge and then after we've retrieved them two values we can return name there we go so let's actually try that up here so we can say new name is equal to return person and then out in new ede and you can take this exact line paste it down here get rid of the birth month and then we can use new age in here and new name inside here so let's run that now ask us what is your name ABA what is your age 23 and then we got ABA 23 which is the same as what we've got before but you see that this situation is prettyy messy we have to return a string variable and also use an output in order to be able to give back two values alternatively what we could do is actually just return back void and then we can say string name and then inage but we're going to have to use references inside here and then have string new name equals nothing and then new inage equals 0o so we have string new name equals nothing and then into New Age also equal to nothing and then inside our function instead of having out parameters we can actually use a reference and we can say a new name and then ref New Age and what that will do is we can just return it like this because it's void instead of declaring a new string name we can actually just assign it to the reference that just passed and because it's a void parameter now and for the return type we don't actually need to return anything so we can actually assign these by reference enter your name ABA and 23 so as you can see it still works fine but let's say we wanted to add another birth month so we' have to take the birth month variable new birth month make it equal to zero and then add yet another parameter ref new birth month and then we need a new birth month inside here ref int birth month and then we need another one from here enter your birth month and then we'd start it inside birth month and then finally we can also return it up here as new birth month there we go AB 23 and then five so we get them values being returned so in order to keep adding different properties to your code you have to make a new parameter a new reference variable and then append the parameters inside the function now the problem that is even though you can have an infinite amount of parameters then this gets very tedious very quickly and you don't want this so let's have a look at how we can make this function exactly the same way just using our new structure you can see that instead of having to pass all of these different things in or return back a certain value we can actually just return back a complete person so all of this can be squished pretty quietly so actually let's just comment all of this out and let's comment out this function and let's have another rewrite so now that everything's gone we only want to be returning and dealing with the person so we can say static and instead of void we actually want to say we want to give the user back a person return person and we don't need any parameters in in this case this is only passed in because it's a reference so we can assign these values back to the original variables but because we're going to be returning a person then we don't need to do that so we can essentially take this code and put it in here and we can say string name now we have an in here and then also an in here there we go so now that we've constructed all our variables that we need for the person what we can do is we can make a new person person person and then person. name equals name and then duplicate this down we say a person. ag is equal to age and finally the birth month is equal to the birth month and then now that we've constructed our person we still got a red underline because we haven't returned anything yet and after all of that we can say return person there we go and now simply in here we could just say person person equals return person there we go and then we can take this console right line here and place it straight underneath since it uses the same properties now let's try and run it AB 235 there you go so now instead of having to make a whole new variable all you have to do is simply just add another one down here so we can just say number this could be your favorite number or anything and we can add it onto here person. number and then here we can paste this down we can say enter your number and then it will be number in here we can paste it down here and change it to number and there we go that's all we need to change and this code doesn't change cuz it's simply calling back the function and we're doing all the hard work inside here so now if you run this enter your name abber 23 5 and finally four and there you go we get the values being returned so this looks a little bit tedious we have to assign each one individually every single time we do it so we can actually use something called a Constructor in order to achieve this result we make the person we set them and then we return it it' be easier if we could have the Constructor that we can assign straight inside here and then just return it immediately instead of having to do all of these lines and then reference each one individually so let's have a look and see what we can do inside here we can have a new function that'll just be called whatever the structure is called then you open the brackets close the brackets for now and this is called a Constructor in order to be able to use it down here we need to make it public in order for someone else to access it so this says that it needs explicit parameters in order to be able to compile it says that it needs to assign name age birth month and number so let's see how we can do that as we've used Constructors in the past for example when we had things like the string Builder we had s SP equals new string Builder and when you make a new something that means you're making a new Constructor so all of these sixes are the parameters that go inside of this but each one of these is a separate Constructor if we control click this we should be able to see them all there we go you see that the class is called string Builder and this is called string Builder and these two names match exactly so to make a string Builder you can give it any one of these as long as your parameters match one of these six you can give it nothing or you can give it some other values and that's the same is true with our current person so what we need to do in this case is we don't have multiple ways that we can constru this in the case of our person we have to provide all of these details otherwise the compiler is not going to like it so we can have a string name int age int birth month and int number now we got our parameters set up we actually need to make use of them in here so because we have name and name and they're exactly the same string by string then in here we can't say name equals name in terms of global and local variables this is global within the structure as it's within these two curly braces and all of these variables are only Within These two curly braces local variables always take presidence over the main one if I double click on this you'll see that all three are referencing this Constructor if I double click on this you'll see that both name references on line 20 down here is all referencing this one in the parameter and not the one up top we want it to be assigned into here so you have two options in this case you could capitalize all of these so then you don't run into this issue and then instead of name equals name it's capital N equals name and that fixes it alternatively if you want it to be a lower case then what you can simply do is you can place this dot if you use this it goes back to the current scope and the current scope of name is going to be this which is within the structure when you use this it doesn't reference the local variables it references the global variables appear so when I double click on this now you'll see that that gets highlighted so we can say this. ede equals ede this. birth month equals birth month and finally this. number equals number so we're just getting all the parameters from here and putting them into these values this might look a little bit redundant but I'll show you why this is a lot cleaner so back in our return person function we have the variable and then we assign them all manually but look how easy this now has became if I comment out this return we can say a return person so now we can reference person with a capital P this time cuz I want to reference the structure directly so after the person we can open the brackets and then start to type in so our first one is name age and the birth month name comma age comma birth month comma and then number comma and then this is not going to like it because we also need to place new inside as I said before when you making a string Builder you have a new keyword and this new means that you want to create a new instance of this you could think of this structure as a template this is the template for something and until you start using that something it's actually not going to do anything so we have to make a new instance of it because it's not already available so we need to make it available through our data type so when we say we want a new person that gives us access to the Constructor if I remove that you'll see we've got one of two now we can create an empty person and that will just make us assign all the values individually but we don't want that we want to use the second path and if you drop the arrow you'll be able to see the different parameters which is the ones we just typed in name age birth month and then number and now that we've returned back this we actually don't even need to do any of these lines right here we can actually just return it exactly like this so now if you run it again you should see exactly the same output 23 5 and four perfect so let's just have a little recap so normally when we're creating variables we use common variables that we've used in the past string in double Flo bull Etc but with the use of structures we can create our own group of variables and then we can use them VAR Ables inside functions and inside our code to make things a lot cleaner and a lot easier so inside person we actually stall four different variables and they can be an infinite amount of variables should you will and you can easily remove them and then remove them from the parameters and from the assignment and then that's it if we use this without our structure then we're going to have to declare every single variable separately and I know this is the same as doing it up here it's actually a little bit more work cuz you need to create a new parameter and create all the the instances inside here and assign the values now the benefit of doing it within a structure is that when you go to do a function look how easy this line is before you'd have to have name age birth month all as references or have them as out parameters and it gets a little bit long and a bit sloppy you only to include the month in here we' have to have another int number and you can see that the parameters are growing if you wanted to store a user from a registration form you might have name address phone number country and the list goes on it can be a very long form and you therefore you'll have a lot of parameters so it's very easy to wrap it around inside a structure and then simply reference it like that and you'll need zero parameters because everything is contained within the data type and then inside here we can ask for the users's details individually store them as their integers and string variables and then instead of using this notation we can now use our fancy Constructor where we can pass it in in this exact order right here name age birth month and then the number perfect and then we can use inside here we can call each of these positions separately and concatenate them together so now that we covered structures known by struct as the keyword let's have a look at classes and how to define them syntactically so we can make a struct called person and we can give them a string name and inage and to make them accessible we'll make them public and we can say public person string name and int age and that means we can assign these values using the Constructor so we can say this.name equals equal name and this. age equals age perfect so let's get rid of our compiler error since we're assigning both the values and then down here we can use it we can say person person equals new person and then have abber and then 23 in the brackets and we can print to the screen person. name and then if use controll D to duplicate that down and we can do age and if we run that right now we should see abber and 23 being printed to the console perfect so as we talked about introduction syntactically the struct and the classes are very similar so let's comment this out so we don't get any compile errors and let's see how this is going to work so of course we're going to get error on this line but once we make our class the error should disappear from here so instead of struct person we're simply just going to have class person exactly the same and because these are fields we can also copy these down so we can have public string name and public int age and then we can have public person and then string name in age this do name equals name and this. age equals age so as you can see this is exactly the same as this except for the fact we have structure and we have class inside here now you see how compile error is gone and if you've run the code we should see exactly the same output there we go now the main difference about classes and about structures is that you don't actually have to give these a default value inside the Constructor if we just comment this one out for a second and if we bring the structure back and we actually remove the parameters from here then we're actually going to get compile errors and it says that the name and age must be assigned before it's returned and stroks cannot have parameterless Constructors now that's a bit of a problem in certain cases you might want to create an instance of something but not actually derive any values so you could actually make these into default values you can have string name equals nothing and int age equals zero and therefore once we place in inside here then there's no problems if you run the code then you will get the output this will be nothing this will be zero and you'll get errors and you won't get any compile errors doing this way but the point is you have to include them and you don't have a choice so if you just comment this back out now what you'll notice about the class person is even if we get rid of it then it still lets us have it of course we can't actually give it parameters since we don't have a Constructor that lets us have parameters but what you can do as well is you can overload this and actually include it as well so you can have another set that literally lets you define both of them and then you can even have another overload that lets you just include the name without the edge and then also another one that lets you include the int Edge without the name or you include both the details so in these cases what you can do is you can store the values up here as the fields let them use a default Constructor or only give it the name or the age or you can actually give it both so when we come down into here we actually now have four different Constructors we can make an empty person we can make it with an edge with the name or with both and what you can do in here is you can say this.name is equal to nothing and then here you can say this. AG is equal to minus one just to default it to a value that's incorrect so after we've got this let's have a look at the different ways so we can give it a person which gives us an empty value so if you run that now we get blank and zero and if we just give it the name which is Aba then we should get ABA in minus one yep and then if we just give it the age you should get nothing in 23 and if you actually give them both then you should get both printed out to the screen and there we go so now we have four different ways that we can create our person with our structure we're only really limited to one since all of these values need to be assigned as the structure is created structures are meant to be used as an extension to a data type rather than almost like a mini management system when we make a class we have so many options of different ways that we can do this inside here and later on in the course we're going to show you how to include functions inside here and then eventually do other Advanced Techniques with classes that aren't directly available structures if you have a basic example where you want to extend something to use inside a function or a data type like starring name and age instead of having to do two return types inside a function then a struct is perfect the second you want to do more complicated things or make it a bit more specific and flexible then classes are the way forward you'll see it very often in games where they have struct position you'll see in video games where they have something like a struct position and they might have int X int Y and int Zed and that's for their 3D position or they might even just have an X and Y or you could have something simple like a rectangle and you can give it a width and a length so now when you use that inside the code you're going to have different flexibilities of the amount with data types that you can store and then when you return that back from a function that will be okay as well since you can use this as a data type so if you want something simple and straightforward then go for the struct the second you want something a bit more complicated and a bit flexible then you probably want a class we go into more different situations inside this cause so you understand in which cases to use what and in most cases you'll notice that the class is more replicable so if you wanted to you could ask the user to enter these details in and then you can pass them inside the Constructor so we could say a console right line changes to a right enter your name String name console. readline and then copy and paste this down change this into a int age and then wrap this around inside a convert in32 instead of enter your name it'll be n your H and then since these are grayed out it means we haven't used them so we can change abber to your name and then change 23 to H perfect so now if you run the code now enter your name ABA enter your age 23 then we get AB number 23 printed out to the screen so just a quick recap Constructors are basically defined the same way you have public followed by the class or the structure name and then the parameters inside the brackets and then you can assign it after without structure you have to declare all of the variables inside the parameter and assign them all down here otherwise you won't be able to run your code with classes we have the flexibility of just including one default function which will just be our Constructor and even if it does nothing this is still acceptable and then we broke it down to multiple sections where you might have situations where you only want their name or their age or you might even collect both to store it if you collect the name then we'll initialize age to minus one just so you know that this is a bad value and if you declare only the age then we'll initialize a to nothing just so you know that it's an empty value and if you accept both then we simply assign both and down here we have access to it we can even make this a little bit better by checking these values so we can say if string is not null or mty of person. name and we can put a not inside here then we can print out this and then the same thing for age we can say if person. AG we can say greater than minus one since we set minus one as the bad value and then we can move this line up and let's try run it now so these two if statements are fundamentally separate from each other one is checking the name and one is checking the age so let's try and manually type these in and see what happens so enter your name let's make this blank and only include the age and let's see if this runs okay so you had no name in the age of 23 then you see we only get printed 23 because it'll skip over this line as you can see if we put a break point in now and just refresh the code we get empty name plus 23 and when we press F10 over this line it jumps the next one because if we hover over this you'll see that it should return us back with false there we go we get strings null or empty is is false so that'll skip over that and because the age is 23 then this line is going to execute let's run it again and do the opposite we could say name is Aba and then age is minus one and then we get ABA printed be not the age there we go so if you wanted to fix these in and type them manually so we can say 23 there we go we get 23 and if we only include the name ABA then we only get ABA printed out and if we include both both of them then we get them both printed out perfect so now that we've created our class we've gave it some fields and we've made our Constructor that lets us initialize it let's see how we can print the details out to the console so we can have a CW tab tab a console right line and then we can say string interpolation name callon space and then we can have our curly braces and we can say person. name we can access these fields using the dot operator and then we can say back/ again for the new line and then say age and the same thing person. AG let's try run that and see what we've got so now we've outputed name and age out to the screen let's see how we can do this inside a function if you wanted to place this in different part of your code then you're going to have to copy and paste this and as we know this is bad for our code because it's j a duplication we want to be able to wrap this inside a function somewhere so let's see what we can do we can have a static string so you can return us back with this that we can output straight to the console and we can say return details and for our parameter we can have something like string name and int age because that's what our class is made up of and inside here we can simply take this put it inside here and put a return before it and then get rid of the person dot since we have an aim and age variables as local to the function so now instead of this line we can duplicate this down take out the contents and we can say return details and then we can place person. name and person. AG inside here let's r on the code so we get exactly the same output but the problem with this function is we're having to type out the parameters manually we have them here and we're going to have to type them again in here and again for the parameters this is a bit of a problem because we've just made our class but we haven't really used it when we're passing it in so instead of having string name and int age we can actually duplicate this method and just comment it out just so you can see it for reference and instead of doing this you can actually just pass in an entire person so now we have access to person and we can bring this back and we can say person. name and we can also say person. Ag and the reason why this method is preferred is if you actually have something else public int number and then you added another one inside here int number and then you said this do number equals number the parameters won't have to change inside the function all you have to do is simply pass in the person and then now we actually have access to doing person. number inside here should we need to if you passing them all all in one by one like this then you have to append into number on the end and then add it straight to here and then also add it inside here as you have like this it's easy to pass the class in because all of these properties above are just simply used throughout the function so now if we just bring this back and let's have a run and see if we get the same output which we do name ABA age 23 perfect so now that we've thought of two functions how to do this we we can manually type in the strings and the integer and any other parameters that we need or we can actually pass in the person the problem with these two approaches is the whole point of having classes and structures of the like is so we can wrap around lots of functionality inside it if you want to send this to another developer for them to use in their project or maybe this is a file that is shared within the projects then you don't want them to include a separate function that is simply outside of the class we want to include the functions inside the class so of course as you know these are functions so inside side here we can also make functions so let's do it so we can have public and we want a string return details and then we don't need to pass anything in the the values that we're going to be returning are these two right here which is technically local to our class so therefore we're not going to have any parameters I'll explain that further in a second so we can take this exact line paste it straight into here and get rid of the person Dot and get rid of the person dot on this side so then we have the name variable and the age variable if you double click on them you see it references these variables and the same thing for age the reason why we don't have parameters is when you call this function as I'll show you in a second you call it directly on the person so the person that you're trying to print has already got these contents inside of them so let's have a look we can duplicate this down and instead of calling return details and passing the person you actually do it the other way around you say the person object dot return details so now we're calling return details inside our person person an object now let's run the code you see the output is exactly the same except now this functionality is a lot better our return details is wrapped inside our class which is the preferred way now we can actually get rid of these inside here and then we shouldn't really use this notation even though is technically correct but you want to wrap all your functionality inside here and just bear in mind that scope is also applicable here return details is within this class which means if you try to run this function inside the main then it's not going to node exist this return details function was able to be used inside here because this was in the scope of the class program which is this curly brace and this curly brace but this return details is only within the scope of this class which means you can't just suddenly use it inside the main so please bear that in mind when you producing these classes and you're trying to understand where everything goes every function that you place inside here is accessible through the dot notation after the object once you've created the class soose person equals new person and then after we type person dot then we'll get a list of all the functions the same way if you have something else just like this and then if you do person Dot and then you see that something has appeared there so all the functions that you create up inside in this class for every person that you make it'll be accessible through the dot notation so just to round up this video you should always make your functions inside your class having them inside the class is the whole point of making a big class and have lots of functionality side if you keep the function that does exactly the same thing outside of the class then if you were to share this file or come back to it in the future then you're not going to understand why you've done this and it's outside the class keeping everything wrapped inside the class is the best way forward in most case scenarios so now we have our class person it's got a name and age a Constructor and a function to return back the details and we can simply use it like this and return back the details like this but so far we've covered how to make classes Constructors Etc and assign the values but the values are only getting assigned throughout the Constructor but what if a different part of our program the user want to change their name update their age Etc then what options do we have so you know we can access our Fields using person. name and then you can simply type equals and then type in another name and we can say person. AG equals 25 now we've changed these properties if we use the console right line and return details you'll see that the values have indeed changed as you can see there it's changed the Harry in 25 this is okay except for the fact that this shouldn't really be possible we should try and restrict this directly by the use of gets and sets so for now we're going to cover fields and how to restrict certain values and later on in the course we're going to go through what properties are so before alter properties got invented we had to use gets and Setters gets and sets are essentially functions that will prevent this from happening so the reason why we can do this is simply because this public word is placed right here if we change it to private it means that name is still accessible within here and here which is only the limit of the class but as you can see it's not applicable here this is why you need the public Getters and Setters so I'll explain that what that means now so we prevent these from accessing outside the class by making them private so this functionality no longer works so what you have to do instead is for every field that you have you need to create a getto and a set a function so in order to set a value we can have public and because we're setting it we don't need to return anything so it'll be void and we can say set name and then we pass in string name and then we simply just say this. name equals name so when someone calls set name and pass in the name like this we just overwrite it so let's see how that looks so if we comment these two lines out we can simply say person do set name and then we can say Harry so this line is directly replaced by this line and now if you run this we'll see that Harry should be changed there you go abber is changed to Harry this is really powerful because what we can do now is restrict the access inside here and make sure that the value contain something genuine we can say if string is null or empty and then pass the name inside there if the string isn't null or empty then we assign it and if it is null or empty then what we can do inside here is we can say else this do name equals nothing and we can keep it blank or we can use string. empty just to make sure that we know that the name has been blanked out if they've entered something invalid if they've entered something that's valid we assign it if it's invalid then we don't assign it and we just initialize it back to nothing and because our options are endless with this we can actually make this into something else we can simply just say invalid name so then what happens is if we try and change this to nothing and we run the code we can see that we get invalid name being printed to the screen and that's a lot better than if we had string.empty because if you had strings are empty then it would kind of say nothing then it looks like something's went wrong if you have something like invalid then that gives you a bit of a bar message so we can have invalid name there so using our Setter Let's us change our name from down here without directly exposing the public if he expose the public then everyone who uses classes can simply change the name to whatever they want having it private and only changing the name within the set name function is very preferable because you can restrict the access and what people can set the values to if they try to set it to something that's not valid then we set it to invalid name whereas before when we did this and if we make this public again we can simply set this to something bad like null null is a very bad value but it still lets us have it and the reason why it's very bad is if you you try to do something like this person do equals and just some empty brackets now even if I just leave this empty the fact that you try call equals onside person. name is going to be a bit of a problem so we can say person object the name property inside it and we're checking if it equals to abber for example but because we've just set it to null let's see what happens you see that we actually get an exception it's a null reference exception because if you hover over name you see that returns back null nulls are very bad in this case whereas if we actually bring our function back and we make this into a private and then if we try and take this value our null value and place it straight inside our set name if you uncomment it get rid of the quotation marks and if you actually try and assign it to null let's see what happens then we're going to get invalid name and this prevents us from breaking our code if a function like equals were to be called on any of our properties inside of name so now that we've done it for our name we can also do it for our age but before we do that we can also call a function called get name return details gives you back these details in a very specific fashion but what if you wanted to do something like this your name is and then you wanted to do person. name but of course you can't do that because name is no longer public so you can't reference it directly so we've got a set name and then now we need to do a get name so we can have public and because name is a string the return type is going to be string and we can say get name and this function is very simple it just returns back name and that's it there's no parameters because all it does is return back a value and in this case it's just returning back name so instead of using person. name in here we can say person. getet name open close the brackets to indicate it's a function but there's no parameters now you see that we have no compile errors so now if you run that you'll see that it says your name is invalid name so let's actually give it a value and we can say hurry again run the code there you go your name is hurry so let officially change it and now let's work on the edge so just following the exact same approach we can have a public void set age int age and instead of just doing this. age equals age let's try set some boundaries on this we can wrap this inside an if statement so as for the condition we want to valid Val if the age is successful so we want to do if age is greater than or equal to zero and age is less than or equal to 150 so this means if the age is less than zero or greater than 150 then this is going to return back false and then it's not going to assign the value and we can simply assign it to minus one minus one is just so we know it's a bad value so now that we've created our set age we can actually make our get age so we want to return back an INT because that's going to be the data type PR age so we do public int get age we don't need any parameters cuz as like the name we're just simply returning something so we can say return age so now that you've made the set age and the get age let's actually use it in our code so we've made our set name and let's say person do set age and we have 25 inside here just like above and then now that we've set the age let's appin this sentence we can say and your age is and then person. getage perfect so let's run the code and see what happens there we go we have 25 and Harry being changed so another little tip when we doing this code our get age is one line and I'll set age as a couple of lines but fundamentally only assigning age so what we can do is we can make these into the tertiary operator so as we can see here this is the condition if this returns back true then we assign age our local parameter and if this returns back false we assign minus one so we can actually make this into this. AG equals if you remember remember the format of our conditional operator use condition true and then condition false so this is our condition that is leading our if statement and if this returns back true then we do question mark and put age in there and then call on if it returns back false then it's simply minus one there we go so this has actually been entirely replaced by this one simple line and we can do the same thing for our string so we can say this.name is equal to string that is null or empty pass the name name inside there and if that is true then we assign it to name and if that is false we say invalid name let's comment this one out and let's see if all code runs okay still hurry 25 hurry 25 and now let's try our bad values so we can try to set the age to 200 and the value to nothing and let's see what happens we get invalid name minus one and there you go perfect so that's working okay let's undo them values and you can see that this has been shorten completely another top tip for functions like this you can actually use something called Arrow functions and if you've done any JavaScript this might be quite familiar so we can have our get ede and instead of open the curly braces at this point we can actually place this Arrow inside so if we comment out this one with arrow functions you can only return back one simple line so because this is only one line we can have return age but our functions don't like the keyword return any variable that you put straight inside here is automatically applied that it's a return type so we literally just put age get age returns us back with age if this is confusing then stick to this approach but this can might tidy up your code because instead of having all of this and all the curly braces for one simple line you can use Arrow function so if you actually copy and paste but first comment out all of these functions you can see how small the code can actually get there we go and then let's actually have a public void set age let's put our R function in and then we can take this one line and paste it straight into here so you can see that these two lines are now being replaced by all of this and of course we need our int age inside here there we go so now we can do the same thing with our set name we can take this we can have public vo set name String name and then have our Arrow function and then simply paste that in you can see that this will get a little bit long now but it's still ideal I've got the code zoomed in but if you put that to 100% you'll see that this code is actually pretty small it's just I've zoomed in just so you can see the code a lot clearer and then finally for public string and we can get name and then we simply just do arrow and then name and you can see that with all this other code commented we just relying on these functions as we just created and you'll see there's no console errors or anything else so if you try and run it you'll see that everything is going okay of course if you don't like this notation and you don't have to include it you can stick with the curly braces I don't use Arrow functions a lot in practice because there isn't many situations where you'd actually use them and even if you do some people might not like them or there might be certain guidelines that you might be following inside a company what I do suggest you stick with is the tertiary operator these are a lot good and a lot better to use since it reduces the cord drastically if we actually remove this and I'll paste it back in just so you can see it for reference inside the resources but you can see that these four functions are now reduced to on one page you can see that they're all got one lines and they're pretty short so let me undo that just so you can see the original code and have it for reference so there's a lot covered inside this video so let's just have a little recap before we finish up so just to start at the beginning when we initialize our person with their name and their age we don't actually have any other opportunities to change their value which is where this comes in you can actually just say a person. name and assign any sort of value you can put anything inside there and it will assign it directly unconditionally the problems of doing this is someone might expose it to null by accident and some wearing your code if you're using something like equals this will actually prevent an exception of course you can wrap this inside a TR catch but this is unnecessary because we can prevent this in the first place it's always best to prevent an exception than to put additional code in like a TR catch in order to catch something that you can prevent in the first place prevention is definitely better than the Cure in this case so having something like a person. name being exposed it's not so much for the integer because integers will always have number values whereas strings they can be initialized to null there is no such thing as null in our age that our default value for an integer is zero so we don't really have the same issue we started introducing the name function and the age function these are used so we can control what Val values get assigned to our local variables and we also have our get functions get name and get age so let's explore how these are made inside our Cass and expand on that and see how they work so first we need to make sure that our variables are actually private they're private so we can't access them just like this if I copy and paste this line above you'll see we're going to get a compile error and this error is because we can't actually use it because as it says here it's inaccessible due to its protection level and the protection level comes from the fact that this is indeed private it's private so it's only accessible within class person so every reference to name can be used inside here just not outside so the only way to be able to change the name now you've made it private is by enforcing this function the good thing about this function is we can check if the value is invalid and then we can star it if it's valid and then change it to something else if it's invalid and then we can wrap this if statement around in a conditional Operator just to make it a little bit shorter and in order to retrieve an name because now that it made it public we can neither set or retrieve it so we have our get name function that simply just returns it back to the screen nothing special here and the same thing for our set age we can check if the age is between 0 and 150 and assign it and if it's not assign it to minus one and then again wrap it around in our conditional operator and then for our get age we can just return age I demonstrated our functions inside here you can take all of these on line functions and actually add them all in one line without the need of cly Braes if you want to return back in age then you simply just type in age just like you can see here and here when you do assignment you want to specify this.name equals but when you're doing returns you just need to type in the variable that you need of course this looks a little bit cleaner and a bit shorter but not Everyone likes this notation so it's completely up to the developer or the environment that you're working in and finally we just have our return details and then we can make use of them just like this by using person which is the name of our local variable for new instance followed by a DOT and then set name set age and then get name and then get age so now that we're dealing with classes it's important you focus on the scope we have a person person here that's defined within the main which means it's only Within These two curly braces so if we had a static void and a function that did something inside here we can't access person inside here if we take out the comment and we try it the only reference we have is accessing the class directly not this local variable if you want to access local variable from inside this function then you'd simply have to pass it in like this and then it'll finally become available as you can see now there's two and it says as a parameter and the same goes for this class above just because we have name and age up here it doesn't necessarily mean that we can magically use name down here if we have something like a static int defined right here then we can use this integer inside these function functions as it says there it's available we can sign that to 10 and it's also down here available and we can sign that one to 20 and you'll see we have no compil errors but if we take this and put it inside our return details function then you're going to get an exception because X is not available within that scope and the functional scope matters inside here as well if you have a string test inside here we can just access it in another function for example the Constructor we can't just print out test as a screen the handy or classes if you want variables to be available throughout the class then you put them at the top we can have that private string test and there you go you see that the compil error is now gone and we can give that initial value and then you can use that to print to the screen Etc and just to note when you have a variable that's called exactly the same thing we have a private string test up here and we can say hello and then we also have a string test down here so let me demonstrate what happens when two variables are the same so let's let's move this into our Constructor so if we run this as it is we test equals hello and then we print out test and then run the code there you go we get hello printed and just ignore this this is from the return details function as we've got in the main down here return details so we've made our new Constructor and then assigned it the value with abber and 23 and then we can get hello printed to the screen but let's say we actually made a string test inside here and we said hi instead of hello then which one you think get use the global one or the local one let's run it and find out it's actually the local one the compiler will always prioritize the local variables over the global variables and this is the reason why you need to type this dot because when you use name it's always going to reference the parameter when it's name on its own use console right line and say name and then if we do after this line and another console right line and we say this. name then these are completely different this one is the parameter and this one is talking about the variables from the class and these are known as our Fields local variables take presidence over our Fields as long as they're called the same thing as you can see now it says it's assigned but the value is never used if you take the string test out then you can see it's now being used there you go hello gets printed out to the screen and there you go the green line has went because we're using it down here scope is very important when you're designing these classes and just to note that the variables that are available inside here are not going to be necessarily available inside here unless you make them public and even when you make them public that doesn't necessarily mean that this is still available magically over here name will only be available through an instance of the person class so if we do person. name now we can see that that's available as our field so that's why that makes it public if we try and make this private again just to return that value back and we scroll down you'll see now we get a compile error because it's inaccessible because it's outside the scope because it's now a private variable so we've covered what it means to have a public or a private field if you have a private field then you're going to have to use Setters and gets in order to work with this field if you make it directly public then you won't need any Setters and gets because the user can just type iname after their public instance so you can have person followed by the dot and right now you can't see name inside here and the blue slittle icon is no longer there the reason why it's not there is cuz there's no public Fields if we then change this to public remove the dot and readit you'll see that our blue square is now back because our field is now accessible and we can assign that to anything that we want the whole point of making this private is your only restricted access so you know what you're doing and the reason why I say that that is if they enter something that's invalid then we want to specify something like invalid if we give them Public Access then we're not going to know and we won't be able to validate what they've entered so in order to do it through a Setter we can make it private create our set function with a return type it's going to take in a string parameter and this string has to be the same data type as the parameter you're talking about call it name or whatever you want it to be and because these two are called exactly the same thing we have to use this dot so we're referencing this name instead of this name in the parameters and here we're just using a conditional operator and we're saying if the string is not null or empty hence the exclamation point then we assign it to name name gets put in this. name and if this were to return back false then we place invalid name straight into this. name and for the get we simply just return a string since that's a data type for name and then just return it back and it's that simple and the same thing for age we validate the age range set it and if it's outside this range we can set it to minus one so as you can see this is a bit long we have our private variables and then we have two functions one for set one for get and the same thing for age so these are called fields and gets and Setters so I'm going to introduce a notion called properties and properties make it easier to do this exact notation so let's now see how properties created since these fields are private we need to make something that's actually public so we can do something like this we can say public string and we can say name with a capital N so now you can see that name and name are not actually clashing and we can assign that in here should we want to and you see we don't need this dot anymore because this is now different it's a capital N so this one always references this and this references this so we need to add something else onto here so if you create them both now you can see we can do age equals age and there'll be no problems with this so now that we've made our two new Fields so now we have our two new public variables which are known as our Fields let's see how we can turn them into properties so if you remove the semicolon you can actually add in some curly braces so inside here we need a getter and Setter just like we had down there but we have a quick Ann notation for it instead of making two distinct functions you can actually create a little section inside these curly BRAC to get and set the name so you got to think of this as a middleman the same way this is a middleman we call this function and this function will affect the name and this is going to be the same principle we make use of name with a capital N but it will actually be affecting the lowercase n variable these are going to be our new middle mans and they will directly replace the gets and sets here so what we can do in here is we can say get press enter go on the next line and make some cly braces and then we can also have a set so this is like our mini get and mini set function just like we've got here by as you can see it's a lot shorter we don't need to give it a distinct name or set the public or anything else we just give it a simple set and get so if you have a look at the compile error it says not all call Path return of value because as it says here this get function is actually a mini function built into this property person. name which is our name with a capital N and then it's do get and this returns back a string so if we actually just type in return this then it gets rid of the compiler error but of course we don't want to return nothing we actually want to return name because remember what I said string name and intage up here is our private field they actually start the data the public string name and the public in age is the middleman that coordinates all of the gets and sets to do with the private variables so for the set just for now we can say name equals and then what do we give it the value of so if we hover over set it doesn't actually give you any indication of what it's going to be so let's have a look if we press control space then we don't also get the list of everything that we can add inside here now it's very difficult to understand what to assign this to when we have set name we've gave it a string name parameter so we can use name down here so what's our parameter in this case well the function itself doesn't actually tell us but I'm telling you right now that the parameter is actually just called value and this is a very default parameter that you'll see everywhere when you doing gets and sets inside a property you don't have to specify value or anything it just gets simply assigned in just like here where we have string name this will be a string value so it will look something like this behind the scenes but of course you can't actually type this in cuz remember these properties are trying to give you a short hand on how to do gets and Setters so you just got to remember that when you trying to set you get the property inserted as value so you can startall that into name so that's it the name is actually sorted now so before we do the same thing for age let's see how we can use this inside the code so we scroll down to our main we have a person person and then we have a console right line that prints the details so we can actually do person Dot and you can see now that it's slightly different if you ignore the age since that's returned back as a field since we haven't done that yet you'll see that name now has a little Cog next to it show only properties this is a new icon that we haven't saw yet so this is our new icon it says it's going to return us back with the string and we can actually execute a get and execute a set straight on this name then we can say name equals Harry and we don't get any compiler errors whatsoever this lets us do it completely so now if we do another console right line and we say person do return details and let's run that and you should see that the name gets changed there we go ABA gets changed to hurry perfect so after we've got person. name let's see how we can also get the value so we can just say string interpolation your name is and then we do person and followed by a DOT and as you can see the exact same list that we got given over here is given right here as well name also says get and set and it returns back a property which is a string type so we can open like this and you'll notice that we don't have the parentheses after it and the reason for that is because the brackets indicate that you're calling a function but a property is just a property it's almost like a variable so you're not actually needing to put any brackets after it because there's no function to call so as you can see this is exactly the same as this in this case we're actually setting the value and in this case we're actually getting the value so let's comment this line out and let's see what happens your name is Harry so that's worked okay so now let's do the same thing for age remove the semicolon add the curly brace we can say get and then return age and then simply do set and then do age equals value there we go so now we got that set up if we return back down here and we see person dot so as you can see now the age is being removed as being a field as we saw in the blue icon it's now being turned into a spanner which means it's a property as shown here show only properties so now you can see it returns back an integer and we've got a get in a set so we can set that to 25 for example and then we can append onto here and your AG is person. AG you see that it's a couple a just as this one is a capital N and now we have get and set available and again we don't need the brackets inside here since this is a property not a function now let's run it we should see Harry 25 there you go your name is Harry and your age is 25 perfect so as you can see now is instead of having our set name and get name which are these two functions we actually have them contained within a property we call this property and it affects these variables but as you can see just as these functions below were a middleman we've now moved the middleman into these properties so as these are only one line you're probably thinking there's probably a better way of doing this and it's a lot quicker for syntax and you're right there is so let's explore that so I said before about Arrow functions when you're doing something like this get name you can have public string get name and then you can simply do Arrow name and this is a very common string function get name that just returns back a value and you can make that into an arrow function by literally just putting back name so we can actually do the same thing but for our properties so these both contain one line so we can actually minimize this and if we just block comment this out we can say public string name and then we can have get and then the same thing with the arrow function when we're doing Arrow function down here you would simply won't use the return keyword you would just type in the variable you want to return so we can say get arrow and then simply low case name and then add a semicolon just so you know that that section is ended and then straight after we can have set and then arrow and then name equals value just like that so as you can see these contents are exactly the same we've actually return them back in a short space and of course here as we got a compile error it just expects a semic callon to be right at the end here there you go and now we do the same thing for our age we can do public int age get Arrow age and set Arrow age equals value perfect so now you can see that this has been drastically reduced if I cut this just underneath you'll see that almost all of these lines are just replaced in a two and you'll see that our functionality will still work exactly the same if we just run the code Harry and 25 is being reassigned over our default variables perfect of course now if you want to add some more functionality inside here for example in our set name we had a little check that makes sure that it's a valid name before we assign it so we actually take this and paste it over here then you see the lines grown quite a lot so what's PR to do is if you're going to have any data inside here that does a little bit of logic then it's best to keep the curly braces since you can have a bigger output and it looks a bit more sensible if you just simply getting and you're setting the variables then you can leave this notation so let's undo this and bring back the original ones in this case there we go and then we can take that line and in the set we can actually replace it here so as you can see this is a little bit grayed out so let's put the semicon at the end and let's see why this is grayed out name can be simplified so what we're doing now is name and all of these variables are actually looking at the private variable whereas if you actually look down here and we uncomment this you'll see that set name if we double click on this one this is the only reference to it which is our private variable appear and the reason why this doesn't need to be used in this case is because our parameter is now called value so it's saying the name is equal to checking if the value is null or empty assigning the value into name if not and then if it is empty then we assign invalid straight into name in the case of our set name our name was our parameter the same goes here if we change this to Value we can change these two for Value as you can see now this dot is actually grayed out and it can be simplified to just simply name and the same principle applies above so let's comment these back out and scroll back to the top so now that we've assigned name there we go we've got our check inside there and you can also leave this on one line if you want you can even drop the curly brace in just so it looks like this instead of having it all on one line so you could do this and this would be applicable as well but the second you start to put it all on one line then it gets a little bit messy quickly so if you leave the outer bracket just like that then you can can be pretty short since you don't need more curly braces so now that we've done that for the name let's do it for the age as well so we had this. age we check the range and we assign the relevant values so let's take that paste it over this we don't need this dot anymore and age in this case is actually going to be the value gets passed in so replace all the ages with value there we go so if the value passes the range check we put the value inside age or not we can put minus one Inside Edge and again we can have the same thing we can use our arrows inside here there we go so now we've got our code drastically reduced so we went from these big functions that have to be defined with specific names over to our properties and they went from really small to just a little bit bigger but now they have advanced connections just to make sure that the variables are okay before you assign it in so now that we've got our properties let's have a look so inside our Constructor we we don't also need to use our local variables which is our private ones directly we should actually get rid of this now and we should always do everything through our properties name equals name and because this is a capital and this is a lower case we don't need this dot in there there we go so what you should do in the return details function is also use the capital n and the capital age so when you hover over these you're actually referring to the property because like I said before these are the middleman to communicate with the private variables you shouldn't need to access the private variables directly you should use the middleman as much as possible so now that we've done that I have one last thing to introduce so if we actually abandon all of this code just to keep it for reference we have something called an auto property and you briefly saw it when we saw it down here so if we actually just bring them back for a second and if you hover over a name down here it says string name get and set in the Cur C brace but you see how the get and set is empty it just has two values inside there and it just ends a curly brace with no actual logic you see in our get we're saying age and our set we're saying age equals this so when we're doing Auto properties what you can do is you can actually make these public again change these to a capital N changes to a capital A and just straight after it you can say Get Set just like that and what that will do is although they're actually made public what it's doing behind the scenes is actually doing this for you it actually has a private and a public for you behind the scenes this is just a Shand these are what's called a auto property what it does is it makes an anonymous property behind the scenes as I'll show you in Microsoft documentation right now as it says here in CP 3 or later Auto implemented properties make property declaration more concise when no addition logic is required and what that means is no additional logic all of these are additional logic if you just simply assigning a value and reading it back just like here then this is no need to write get name and set name if all you're doing is getting and setting it if you're getting and setting it but there is a certain amount of logic as we have here we essentially have a conditional operator that's making a subconscious decision about what to assign the name to but if you just simply assigning something like this then an auto property is perfect they also enable client code to create objects when you declare a property as shown in the following example the compiler creates a private Anonymous backing field that can only be accessed through the properties get and Setters as you can see here just like in our example we have public int something and then get and set and then they have a public in something with the get and set as well and they can use it just here to access it directly and because they're simply just assigned and getting the values and there isn't any additional logic then this is the best way to do it and you get as it says here an anonymous private backing field so this would be the same thing as doing this private string name and private int AG so once you do that and you make this into the get and set properties which are these two right here this and this line together make a property what the auto implement the property does is actually combine this line and this line together and make the private one behind the scenes so the programmer doesn't see it but it will be applicable when the program runs in the compiler and then you only get publicly exposed with this parameter which will be our name property so it will actually make the private for you if you just keep it like we had it a second ago just like this so if you leave it like this it will actually create the private variable behind the scenes as it says here it's Anonymous backing field and it can only be accessed through name and age and as you can see none of our code has actually changed all of these still function okay and if we run the code we should still get Harry and 25 so just to sum this video up since there was a lot covered the bottom line is if you're going to have any sort of values that require any logic then you should use normal properties if you're simply just going to assign and get the value and it doesn't matter and you have no control over it then you can use the auto implemented properties since that will do the same thing with less code using the gets and Setters is the old way of doing this and you should always use the properties going forward Getters and Setters are very helpful to know just so you understand what they are and why they exist but you should not that properties are the best way forward properties give you access to doing the same logic as it says inside here if you do an auto-implemented properties then you're not allowed to use the logic inside the set or the get so if you don't want to do any logic then don't use the AL implemented properties only use the normal properties to make a get and Setter you just do set name get the parameter and assign the local variable and the get just returns it getting back a property you want to capitalize your private variable if you had private string name with a lowercase n you want public string name with a capital N you get the name and then you can set the name with some sort of conditional operator or any if statement or anything inside here and the same thing goes with the age you can have a public int age with a capital a and a private end age with a lowas here you can get the age and then set the age with a conditional operator again or any other code if you don't require any logic like these two lines indicate then you can simply just use the auto properties as demonstrated above here and they can be used quite easily throughout the Constructor and our functions and even outside the function when the user is trying to call them but one thing that we haven't been able to solve and you may not have noticed this as a nuisance the problem is when you trying to return details about something we're having to call this function every single time if we have an INT age for example and made that equal to 23 and we did consle right line and simply placed age inside the brackets we don't have to do anything like this because it simply just prints the value out if we run the code you'll see that it simply just says 23 this should be pretty simple for our person as well but it's not we need to call return details every single time we want to print the properties and if we don't do this the only way to do it is is by making some string interpolation and we can say person. name and then also include person. AG Etc and then that can print out to the screen just like that of course it doesn't have the same format in but we can also just take this place it straight inside here add our person dot before them person Dot and there you go then you get exactly the same output as call and return details but of course you don't want to do this every time and you certainly don't want to have to type type in return details function every single time as well you want to keep it as just person now of course this is not going to work straight out the box let's try run that and see what happens so we get string override. person and what's going on here is it's saying namespace is string override and then it's a class person so it's just printing out this person object but it's not really doing anything because we haven't really told it to do something so what we can do here is we can actually override the two string method so let me explain so let me set up a couple of examples just to show you what's going to happen at the end so right now we call return details to return these details what we can also do is say do two string and then we can also do these three options return the details convert it to a string or just print the person straight to the console at the end of this little section we're going to make all three of these print out the same values so let's have a look now two string and printing out normally these two lines right here are actually doing exactly the same thing behind the scenes when you place anything inside these brackets inside a console right line it will try and convert it to a string anywhere so whether you put to a string or you leave it as person the console right line function will still accept it so let just comment out the age for the time being in order to make the two string function work as well as just ping person inside the brackets we need to make a special function which is an override function so let's have a look so just underneath our return details still within the scope of the class would say public and then override after we press tab we can follow it by a space and we can see the functions that we can override so in this video we're actually going to cover two string and equals get hash code will actually serve as a default hash function if I show you the documentation it says here a hash code is numeric value that is used to insert an identify an object in a hash based collection this is normally used when you doing hash functions as it says here and for the time being we're not actually going to be using this right now so the two we can do are two string and equals but as you can see our two string is available right now we'll cover equals as an extension in a minute so let's double click on our two string and we get this little template placed in if you don't want the template then it's just an override it returns back a string since it's converting to string it needs to be this exact notation if you drop the T then it's got nothing to override now you go be a compil error cuz there's nothing to override itself so play two string the capitals there's no parameters passed in and then we're going to be returning something so the thing that we're going to be returning is exactly the same as our return details function we actually have two options here we could say return and then return details so what that will do is it will go to this function it will call this function grab that and essentially place inside here and then return it back to the console in the ideal world we don't actually need this return details function so we could comment it out but I'm going to leave it in just so the demonstration doesn't break down here so we can take this and place it straight inside here now we have two functions that essentially do the same thing thing but the advantage is this function is something that needs to be called explicitly do return details whereas this function the two string override actually just gets called naturally without having to add any extensions so if you run the code now you'll see that now the all equal exactly the same value we get three sections that have this maybe we can place back SLT instead just so we can have them all in the same line there we go so you can see all three are exactly the same so what we can do now is if we comment this option and we comment out this function we don't have to include two string if we don't want to we can also comment this one out and we can keep it just as person so as we do when we declare the integer we say inage equals 23 and then we simply print out and this is exactly the notation that we want it should really be this simple there you go one line creates the person and one line with just a variable name goes inside the brackets to print them out the same thing here person person age and age and let's run that code now and there you go you get the person printed and the age printed exactly and straightforward as you may think it should be so now that we've done that let's explore what the equals function needs to be done let's make another person we can say person test equals new person and we can have hurry age 23 now we don't need to print them out in this example we just need to demonstrate this equals function so if you remember with strings we can have a string called Abba for example and we can say do equals straight after it we can say if ABA is equal to Harry then we can do something inside here what I'm trying to demonstrate is once you've got an object you can place do equals and then you can compare it like that so you can also do that with our classes so we can say person do equals and then equals to test and in here we could just say same let's try and make these as same as possible and see what happens so let's keep the name exactly the same just like that and let's copy the 25 down just like that so now these two are instantiated exactly the same way let's see what happens when we've run the equals then we don't get anything printed which means they're not the same so because this doesn't automatically tell us that these two are exactly the same we can override that and provide our own functionality just like we did with the operate overload we override equals we get passed in an object and we need to check something inside it so let's see what we can do inside here so in order to check if something is equal to another thing what can we do so we have a name and an age if this one is the same as this and this is the same as this then two people are exactly the same so let's try that out and see what happens so we can say name which is the property inside the class that we're currently inside and then we can use equals because this is just a string parameter and then we can say that equals to objectname but you can see we've got a little problem here this object is very generic it's just an object every class that you create is derived by an object what that means is every class or integer or double at the end of the day is also just known as an object through inheritance which we'll discuss further on this course but just know that everything inside C is always an object somewhere down the line so what that means is we have to convert it from an object to our custom class which is person in this case so we can use this thing called casting so we can say person person which is just Define a new variable and we can make that immediately equal to object as person so what we've done here is we've said our object which is this parameter is currently an object right now we want to cast it as a person which is kind of like converting into a person and then placing the values inside here so now if we get rid of this comment and instead of using object we actually have a new local variable called person so then here we can say personname there we go now we have access to the person property since we've converted this object into a person and of course we know that we have name and age available so if the name is equal to the person. name and the age is equal to the person. age then we must have a match and of course you want to keep using the properties we're going to use a capital A and there we go so we run the conversion on one line and then we check if they're equal to each other now in this specific case you can actually pass anything inside here so let's try it we can pass five into idea and as you can see there's no compile error cuz like I said five is just an integer which is an object at the endend of the day if you make it a double that works as well there is literally no compile errors and even if you put M to make it into a decimal again there's no compile errors because they're all objects at the end of the day so let's pass Tes in there what you will have to know is if you do accident pass in a double for example like this you're going to hit an error here which will be a runtime error it will try and convert it as soon as it hits this line and obviously you can't convert a double into our person so what you could do just to wrap it around you could say if the object is a person then we can proceed with a conversion just like this and then what you can do for safety is just outside of this you can actually just return back false just so the user knows that this isn't equal to each other so if the object is a person then we convert it as a person is is used for checking and as is used for converting is this object a person and if it is then we try and convert it and then return back if they're equal to each other and if we accidentally pass something in that's not a person then we just return back false so let's just demonstrate this first not the same so let's just save five inside here it says not the same so let's actually go into this place a break point and let's run it again hover over object then we get five if we place this straight inside the watch you can see object is person is returning back false so it's skipping this entire function and going into return false and then it's returning back false so we get not same let's stop the program change this over to test and rerun it using F5 and now we can see object is person is actually set to true so now if we put the object inside here you can see that generically it's an object right here it says object so what we can do now is we can place person and down here as well you see that person doesn't exist but if you just give it a second it we change this to just the p there we go so obviously the person doesn't exist cuz we're only up to this line we press F10 and F10 again so now it's create a the variable and F10 wants to skip over it and now you can see the object has went from type object to type string. override. person string overwrite is the name of our namespace and do person with a capital P is the name of our class now you can see that the object and the values are exactly the same 25 ab and 25 AB as you can see right here so now both of them are exactly equal to each other so when we check this name here is Aba name here is Aba age 25 and age is 25 so this must return back true and we can check that by highlighting everything dragging and dropping it down here and we can see it says true there so when it returns back to our code it's going to go and print their same perfect there you go so that's it for this video but let's just have a recap before we wrap up so before this video we'd always print the details out like this person. return details but obviously we don't have that function anymore so let's just bring it back quickly there we go so we use return details and this is just a bit long have to do this every single time if you want to print the details of the test object as well you have to test Dot and then return details again it'd be so much easier if we could simply just use it like this as you would do with a normal variable like an integer double A String Etc and now it's made possible by using our public override string two string function it will contain exactly the same contents as our previous function except we won't have to go through an additional function just to print out the details we can override the two string and then we can call it straight in the console like this and finally when you're doing equals inside an object you can actually build in some custom functionality we can convert the person using object as person but first before doing the conversion you want to check if the object is indeed a person type before doing the conversion this will give you a runtime error on this line so let me just demonstr that before we continue so if I comment out this one and actually just change this into 5D and then let's press into the code right here it's going to hit this line if I press F10 then it's going to try and convert it but you're going to get back null and then if you run the code again then you're get an exception thrown here you're going to get a runtime exception because it's a null reference we're trying to run the equals function on something that is null which is right here null reference exception so you shouldn't do this you you should also make sure that these are correct values before doing it this is a form of error checking if you don't do this then you're going to have to wrap this inside a tri catch and it will look something like this and the cord will be considerably longer you can place these two lines inside here and then place your cat inside here etc etc and you can return false inside here but as you can see the Cod is a bit more complicated now and there's no reason for this extra complication if you can prevent it with an if statement so undo that so what's best in this case is to say if the object is of type person then we can run the conversion if you run the conversion and it's not of type person then as you can see it's going to return back null for the person and then when you run this line it's actually going to return you back a null reference exception at this point but anyway the whole point of this equals is to check if two objects are going to be equal to each other so we keep this back to test because this is a custom classes you can't just simply do person equals equals time test and assume that that will just work these aren't buil-in functionalities for custom classes we covered operate overloading where you can actually overload what you do with the equal sign but we didn't cover the dot equals which is what we're doing today in this video as well as the two string this is a different kind of overriding because in the other one when we're doing operator overloading that's specifically an operator that you're just changing the parameters of whereas this one is a strict override of a function equals and the functions two string this will make it easier to print your custom classes out to the screen as well as comparing them just like this person. equals putting test inside the bracket is a lot easier and quicker and you can build in your own custom functionality if you only had the age in there then you can compare the age maybe have a lot more properties and you can always just chain them inside a big if statement that's fine as well but the point is you have full control over how you compare your custom classes maybe you had a list of names inside a dictionary for example and you wanted to add a new name or a new age or a new user to this dictionary but first before you add a new user to the dictionary you want to check if the user already exists so maybe you could have a system where it uses the equals function and it Loops through all of the dictionary items and it checks if all the values are not equal to this one if you didn't build in this functionality so you could do the do equals function then you won't be able to determine if this one is equal to this one and now with your equals function overrided you can now have the functionality to do so thank you for watching this C course I hope you found it helpful in your journey to becoming a proficient C developer if you have any questions or need further clarification on any topic we have covered please don't hesitate to leave a comment below and I will do my best to assist you for those of you who want to dive deeper into C consider checking out my udemy cause you'll find more comprehensive lessons and Hands-On exercises to enhance your skills remember practice makes perfect keep coding and exploring and I wish you all the best on your programming Journey

Transcript for:In-Depth C Programming Course Summary

Transcript for:
In-Depth C Programming Course Summary