hello in this video i'm going to talk about flowcharts and the main symbols and go through a few examples of flowcharts in action so you would have definitely come across flow charts before but maybe not in quite a formal way so a flowchart is a visual way to show the steps involved in an algorithm now the word algorithm you might have heard of but again might not know what it means formally an algorithm is a set of instructions which solve a problem a computer program is an implementation of an algorithm so we use them all the time in real life and in computer so visual meaning they've got shapes and we can see them as opposed to just written text now there are four main flowchart symbols you need to know the top left one starting with that one um is just a start or end symbol you generally just write start or end and it will show you where to begin and where to end in your algorithm a rectangle is just a process being carried out you usually write a little description of it so a typical instruction will get written in a rectangle a parallelogram is really a modified version of a rectangle is just an input or output if you just used rectangles that would be fine but if you really want to be clear that it's over an input so asking for something or an output showing something you'd use a parallelogram and maybe the most important one is a diamond which is a decision to be made now this one is where people go wrong we should ideally only have two options so it should really be a question which has only two responses a binary question so for example if you said what is your name that's not really suitable but something like are you above 180 centimeters that would be a either yes or no answer which would be suitable so you've got two pathways coming out of there one for true or yes and one for false or no and all of these are connected with arrows so let's look at an example flowchart this is one i made so have a quick look at it and see if you can figure out what it's doing because a common question will be trying to interpret a flowchart so we can see we start here and we end up right we start by asking do you have an account if you don't you go to a sign up screen and it works its way back round to re-ask for question if you do have an account you're going to enter your username and password this is an input box you then check do the account details match if they don't you loop back and re-enter the username and password if they do match it makes a success and the program ends so as you've probably figured out this is for a you know a website where you're logging in with a username and password fancy word is authenticating if you are authenticating you are um you are checking somebody is who they say they are now you might do this flowchart a little bit differently it's not perfect but hopefully you can see how i've used these decision shapes and they are yes or no and the arrows hopefully are relatively clear the direction they're following make sure every arrow has a an arrow head right you could just do a straight line make sure it's got a direction and it's fine to loop back and you often do this when you want to repeat something just make sure it readjoins at the place you want it to like here and like down here now this symbol bottom left i didn't actually show you this one's a bit different to the success box because i've got an additional two lines inside this process rectangle now that is sometimes called a subroutine and you'll sometimes see that when it is its own program so for example sign up screen could be a whole nother program this flow chart would get really really big and really complicated if i included all of the steps for this sign up screen so this little red tank with the lines through it can often be used to symbolize another flowchart somewhere else so let's say you wanted to actually show that flowchart you might start with the sign up screen name so it should match up so sign up screen in my rectangle matches up to the words in my start symbol and what you might do you might sign up and you might first of all enter your username and password right if you sign up for a website you've got to give it a username and password then for example you might as a web developer need to check does a user exist already because if somebody exists already with those details you can't then register a new person so if a user does exist already that means they've got to go back and re-enter their details again if a user doesn't exist already with those details you should save the details to the database for example and that might be it you might end at that point but hopefully you can see why this flowchart is relatively simple but would really over complicate my other one so you will occasionally see symbols like this used to break up complicated flowcharts but the key thing is are you able to draw simple flowcharts do you know what the symbols mean are you able to interpret flowcharts on a page that is the key things you need to know for this topic