Transcript for:
Comprehensive Computer Science Lecture Overview

[Music] welcome to another computer science video so we should be live if you're watching this um right now um so this is a live stream but again i will upload this after the live stream if you're interested so this is my first video with the facecam hopefully you will enjoy these types of video hopefully you'll connect more with these types of videos um or um so yeah anyway uh today we are gonna be having a look at computer science and we're going to try to cover the entire syllabus so there's about eight chapters okay so we're going to be trying to cover all the eight chapters for the theory segment or the theory part okay so here i have the official cambridge igcse textbook which i've linked down in the description and i've called it notes so you can go and check that out right now at the same time if you've already revised whatever i'm going to be going through this video um there's some pause paper questions plus people question videos where i go over all those questions um you can have a look at that so you can just improve your accuracy and practice more and more if you're confident with what you've learned but if you have not again you can finish this entire live stream and then go and try to solve these past paper questions for extra practice anyway so we're going to start and we're going to start with the basic now i've done many live streams covering many other topics that i'm going to be covering up in this live stream but i thought um you know we start fresh and do um everything so as you guys can see here we have section one i'm gonna be doing section one in this live stream we have chapter one chapter two chapter three chapter four uh five six and seven as you guys can see and finally we have eight now in the future i will be maybe making a practical video um or the segment where we talk about the computer science in terms of practical uh in terms of practical sorry uh where you know we have pseudocode we have python code um and a lot of stuff flow charts and everything related to that truth tables query tables and everything related to that so maybe in the future i will be making a video focusing all on just that but in today's live stream we're gonna have a look at the entire paper one so paper one initially is only theory okay so where uh we have only theory 75 marks only theory so that's what i'm going to be covering in today's live stream so this is great revision um for your upcoming exams okay so we're going to start with the binary systems and hexa decimal systems okay so here are the eight chapters for the section one so we're going to be covering all these chapters in today's video so stay tuned for that we're also going to do some examples and um you know work our way up to chapter eight and hopefully finish the entire paper one um content okay so let's begin and uh let's start with the first chapter binary systems and hexa decimal so i'm going to take my pencil out and uh we'll be also you know reading and telling you some information about this now first thing we are going to be having a look at is binary systems and extradition so initially what this basically means that a binary system is basically used in the computer so is the hexadecimal so in basically in chapter one we're having a look at what the computer understands again we use a language called binary systems now before even we go to the computed language let's have a look at our own language okay so our we say number system let's have a look at our number system because when we're looking at binary systems hexadecimal systems we are only dealing with numbers okay no letters nothing like that of course in hexadecimal we will come to letters but you know they are equally um you know they can be changed to numbers okay like later on you get to know hexadecimal a basically means 10 okay so technically they are basically numbers so we say these are called number based systems okay and they're different types of number based systems and we're going to be having a look at three number based systems in chapter one now if you don't understand what i'm talking about you will in just a bit i will be explaining explaining the number based systems um you know step by step so let's uh go back to where i was talking about so i was basically saying uh our own number system okay our own number system we say in computer science terms it is called daenery number system okay so it's called the daenery number system now if you have noticed okay and you should know this that in our number system we only have about 10 numbers we have only ten numbers zero one two three four five six seven eight nine and ten ah sorry till nine only after that all the numbers after that is simply comprising between these ten numbers okay that means for example we have zero one two three okay to construct 22 i'll need two and two which i talked about in the ten in the ten numbers so the identity system is the number system we use okay the computer does not use the same system okay later on we'll get to know why okay but in simple terms what uh this textbook gives an example of is a computer is comprised with so many switches okay and in simple terms we can say okay maybe let's assign one switch a number okay so for example you know the to switch on something we can say it's represented by one and two switch or something is represented by zero now let's have a look at the number based systems and again if you don't understand yet don't worry i will explain everything just in a moment okay so here comes the actual part that you need to know binary systems and hexadecimal systems so we start with binary systems okay binary systems have only two numbers okay there are only two possible numbers that it can have you know the way in dinner we had only ten numbers zero to nine so with the binary system we have two numbers and those two numbers are zero and one now this textbook or this note is giving example that one will be maybe the position on and zero will be the position off later on again you know as we will develop those skills we'll get to know about something called registers okay and we're going to have a look at all the uses of binary system users of hexadecimal system everything related to this so as an introduction i want to tell you about binary systems and hexadecimal so this is chapter one and let's have a look at this okay so here it is the binary system okay so we know the resistance zero to nine okay hopefully i explained that well hopefully you understand that okay that means that in our number system we have only ten digits zero to nine okay zero to nine all are those digits okay after that we're just basically using them again and again so in relation to that we have the binary system okay the binary system is comprised of only two numbers okay the two numbers zero and one okay so we say the binary system is based on a number two okay the way the identity number system is based on the number 10 okay so binary system is base two okay we say that it has only two possible values therefore it has a base two okay so let's give an example of how a binary number would look like okay so right here if you guys can see this is how a binary number would look like as you can see there are only two numbers zero or one so there are only two possible values that can be you know used either zero or one okay so hopefully you understand you know the difference between binary and generally okay so uh an example of generally would be 56 okay just a number system any number in our number system is generally so for binary it'll be one one zero one one one zero later on we'll get to know why we do this uses of this so don't worry about that right now so in simple terms even you know for the sake of just explaining it right now the binary system is basically used so that we can communicate with the computer okay because the computer cannot understand tenerife okay again we'll also i'll also tell you about hexadecimal and its uses okay so let's start with the first one converting from binary to dendry okay remember binary has only two values while then already has zero to nine okay so let's see how we can convert from binary to january okay and this is a very common exam questions and you will never miss number system conversions so you better understand this right now okay so the best time or the best way to explain something is by doing an example so i'm going to be doing an example right now okay so let's do an example so uh for example i have um let's use uh their example okay um i'm gonna try to get an example so we can use now the method i use is method one and i'll be explaining method one now also method two briefly go over but i prefer choosing method one but some people prefer method two i i find that method two sometimes you can find uh you know or you can make mistakes uh but method one you know is sort of more you know reliable according to me but again uh you can see for yourself and decide which method works for you so the two methods to convert from um uh generally to fine oh sorry i missed binary to that okay simple um okay so let's have a look at binary to generally okay so i'm going to use a activity 1.1 a i'm going to do a so i'm going to write these numbers once again like that 1 one zero zero one one okay this is an example of a binary digit okay hopefully you guys can see um let me zoom in so you can see better okay hopefully you guys can see okay so here we have the value okay zero zero one one zero zero one one this is my binary digit okay this is my binary digits and i want to convert it into dendrite digits okay and general digits is our number system so how can we do this okay so the first step you will want to do is just simply put two over each number okay and uh just simply follow this step okay put two on top of each number okay once when you put two on top of each number from the right-hand side to the left-hand side start with 0 to the power 2 to the power 1 2 to the power 2 2 to the power 3 2 to the power 4 2 to the power 5 6 and 7. now in computer science for these number systems every time you have zero okay so every time okay i'm going to choose another color or let me highlight or sorry let me choose another color okay um every time okay every time you see zero okay every time you see zero cancel it c zero cancel it you see another zero cancel it and cancel it until you're left with only once then what you simply do is the number above the one like for example two to the power zero okay two to the power zero two to the power one to the power four and to the power five okay two to the power zero anything to the power zero is one okay two to the power one is you know two okay and you can see i i'm only looking at the values above one okay so i'll finish this and finish this for the next one right here i'm doing plus two to the power four okay now usually in a computer science exam you're not allowed to you know have calculators so you'll have to do this all mentally and then you add 2 to the power 5. okay so 1 plus 2 plus 2 to the power 4. so what simply you do is 1 plus 2 plus you have to find 2 to the power 4 okay and with this table right here you can memorize it 1 2 4 8 16 32 64 128 you can see 2 to the power 4 is 16 so i'm going to add 16 and 2 to the power 5 should be 32 okay so 32. now i simply add the values and uh you'll have to use some you know the old ways uh you cannot rely on your calculators so you have to you know do it the long way okay so 48 um so the answer will be 51. okay and you know 51 is our number system you know we say 51 we say 1 2 3 51 is our language our number system so that is how you convert binary today okay hopefully you understood that um you can play that again so that you understand and this applies for any binary to them finally let's move on to generate binary so now how can i move from 51 to the following number on top okay now our method i like using is similar to what we just did okay what you simply do is write 2 to the power 0 2 to the power 1 2 to the power 3 2 to the power 4 2 to the power 5 to the power 6 and you can memorize what this means like to the power 0 i'll always know it's 1 this is 2 um this is 4 this is uh okay sorry i missed 2 right here so i uh sorry um i'm gonna i'm going to erase it now you can remember these numbers in order okay and uh you remember these orders 1 2 4 8 16 32 64 128 256 500 something okay simply what i'm doing is 2 to the power 0 1 2 like that going okay this is the same numbers that require here same numbers okay so what i'm basically doing is now i need to convert from binary sorry from generally to binary and what i do is i make combinations okay this this method can take some time but i assure you it's the best method okay for example i want 107 two binary okay 107 to binary so the first thing i'll do okay um you know let's add 64 okay and let's add 32 so 64 plus thirty two okay this will be 96 not your tweet one or seven ninety six let's add maybe eight okay it's at eight so 96 plus eight uh that should be um about 104 but not yet reached one and seven we need how much three more so i can do two and one okay which is going to be three and that will be one of seven so what i'm simply doing i've picked which numbers i've picked 64. i've picked 32 hopefully you can see this um i'll pick 64. i've picked 32 i've picked eight i picked one and i've picked two so everywhere of whatever numbers i've picked i'm gonna put a one below it okay because remember we only add the ones with one okay so i've picked 64 so that'll be one i'll pick 32 that'll be one i've not picked 16 so i'll be zero i picked eight i'll be one four zero is this this will be the binary if you've noticed this number that i've just written is the same thing as this number right here of course there's a zero in here uh but you can just put the zero it wouldn't matter because we don't count it so this will still be correct okay so that's how you convert from the um generally value to the binary value okay now let's have a uh you know let me introduce you to the hexadecimal values okay so finally let's have a look at hexa decimal values okay but before having a look at hexadecimal values let's have a look at a measurement of the computer size okay or the computer system now in computers we have um size of course okay because nothing you know all devices have size okay measurements okay um so what this basically means that even if you have or if you're watching this video on your phone you know that for example your phone has a capacity of 64 gb that's the max and then the phone gets filled up so using that same theory a computer also has that any device actually as that okay so in computer science you need to know the memory size you need to know the memory size of the computer system okay so we start with kilobyte as you can see one kilobyte is equal to 10 to the power 2 to the power 10 sorry bits we have a megabyte we have a gigabyte terabyte and flossley a petabyte okay so in computer science you need to just know these um is it five yeah you need to know these five kilobytes megabyte uh terabyte and petabyte okay you need to know those five okay so there can be a question as you can see right here i'm gonna highlight it so you can have a look at it so let me just highlight it it says that um to give an idea of these skills a typical okay here a typical data transfer rate using the internet is 32 megabits which is 4mb per second okay and then it says so 40 mb files will take 10 seconds to transfer this statement right here tells you about what we're going to be talking about okay this is sort of you know an example to a question okay so for example it tells you these are usually very one-mark questions um very easy questions okay you need to just think and you get thoughts okay so here we're saying that a typical daughter transfer rate of the internet is 32 mb okay megabits mb okay typical transfer rate um is 32 megabits and it's saying that is 4 mb per second then it asks you how much will a 40 mb file take you remember 4 mb per second so you simply do 40 divided by 4 to give you the number of seconds it would take to transfer the entire a very simple math and um most likely you all are doing bats so this shouldn't be a problem okay so the answer would be 10 seconds to transfer very simple questions and um you just need to know those five which is kilobyte megabyte gigabyte terabyte and peta byte okay hopefully you understood that let's move on to finally have a look at some uses of binaries okay here is now where you know we further develop on what we were talking about before okay so previously i was talking about the binary digit the binary value and why do we need binary value and that's a big question why do we need binary value now the binary system can be used in registers i was as i was previously mentioning as you can see in chapter four we're gonna be having a look at more um you know gonna have a focus on registers just as itself so we're gonna have a look at that but simply registers are a group of bits that are simply told to do something and they perform it and in those registers we use the binary values we use the binary system the binary digits okay and now so we use registers and for example i can give you an example one is for on zero is for off okay a very very simple example okay so that's just a simple um you know example and questions are usually structured like that for example they give you sort of a diagram like this one right here it says you know there is a wheel that rotates whenever it's one or zero and you know you have to make a binary value digit or whatever okay so every time it's one it means that it rotates every time it's zero it doesn't rotate something like that and it's quite simple um this should be a very easy question again if you want to practice on these types of questions i've had past paper questions and you can also request for a past paper question that you want to be solved just down in the comments or now the live stream you can do that okay so let's move on now um finally let's move on and let's have a look at the hexadecimal system okay because better look at the binary system now let's have a look at the hexa decimal system okay so the hexadecimal system what is the hexadecimal system okay the hexadecimal system is like you know kind of related to binary system so then you ask yourself why do we need to know it then okay so i'll tell you this first of all hexadecimal systems are much easier to use compared to binary systems okay because if you've noticed all those digits 0 1 1 0 1 1 1 0 0 1 it's complicated okay and a human would not remember it of course okay because right now the example would you remember what i did probably want okay because there's so many values even though the only two numbers there's so many it is very hard to work with that means that if i even make one number as a mistake when inputting you know i wouldn't be able to find the mistake and therefore we come to the fact of hexadecimal system which is a much easier number system that we can work with okay so let's have a look at the hexadecimal system okay let's have a look at the hexadecimal system so the acid decimal system is base 60 okay we had the binary system with the base of two we have the identity system with the base of 10 which is our number system and now we have the hexadecimal system which is a base of 16. okay with a base of 16. so what are these 60 numbers then okay and here is the table that you will be needing okay so as you can see here is the table and uh you need to remember this table okay so the table starts with the binary value okay you can memorize the binary value but i will find i'll tell you an easy way to memorize this later on when we're having a look at some conversions from hexadecimal to binary binary to x a decimal and so on so forth so let's start with the hexadecimal value zero okay general value will be zero hexadecimal value one will be one okay so it'll be all the same till nine but what changes is when it reaches nine after nine we don't write ten we write a okay so it'll be a b c d e f okay so if i zoom out out um you should see the whole table itself that is the whole table okay so you can stop we start with zero one two three four five six seven eight nine then we have a b c d e and f okay a being 10 b being 11 c 12 d 13 e 14 and f 15. okay quite simple very easy to memorize so finally let's have a look at some conversions okay let's start with binary two hexa decimal okay so we're starting with binary two x at decimal and from hexadecimal to binary so let's start with the first one from binary to exodus so here are the steps you're given a binary you need to convert it to x decimal what do we do okay so i'm going to rewrite this once again so i'm going to write this binary value 0 1 0 1 1 how many ones are there one three four five three and there are four zeros uh yeah so right here is my binary value and i need to convert it into hexadecimal what am i going to be doing the first thing i'm going to be doing is splitting these numbers into four so one two three four boom one two three four boom okay i've done that quite simple no one should be confused at this point then we move on and do put two on top of each number oh sorry not two um you put these numbers one two four eight the same for the next one one two four eight and the next one one two four and eight okay so i've repeated it for the three segments one two four eight one two four eight one two four eight i need to convert this into remember hexadecimal how do i convert it to hexadecimal now i have this small value looks like this be one for example and hopefully we should derive to that the next thing again remember the principle whenever they're zero cancel it okay so whenever it's zero cancel it this only works for number system so please don't cancel zero and other stuff okay only works with number system so zero cancelling zero cancel it zero cancel it and then zero cancel it now we simply just have to add the numbers so um i'm gonna write in black okay so right here we have only one number left is one okay the next one right here we have two plus four plus eight which is uh eight plus two ten fourteen and here is three plus eight which is uh what um 11 right now this is not hexadecimal because remember hexadecimal 11 there's nothing like 11 there's nothing like 14. so remember without table 11 is b so b 14 is e and then one remains one so this will therefore be very simple very easy okay so that's how you convert from um binary to x now how do i convert from hexadecimal to binary same thing you divide the hexadecimal uh code and you convert it into binary for example we have the example four five a you split this into three parts okay a okay then write one two four eight and you need to make a combination that will give you a which is ten so remember two plus eight so one on uh below two one below eight zero zero okay so this will be the first segment of a you can see right here that is correct and then you do the same others are just now quite simple if you don't understand i've made an entire video on this um so if you want to have a you know if you're confused in any of these topics that i will be having a look at in the live stream again anytime in the comment section you can ask for some help and also you can watch my other videos on the same topics and i believe the first video i ever made was on this on the number system so you can have a go and have a look at the following okay but again you know this is quite simple so you should understand it very quickly okay let's move on to converting from hexadecimal to dainery and then again generally to access so let's start with hexadecimal to generally how do i convert a finger of 4 5 a into our number system now again you need to remember these numbers 1 16 2 5 6. what and usually um in the igccs you are usually only given about three values for the um for the hexadecimal um very rarely would you ever get four digits in hexadecimal if you do it's quite simple and very easy numbers maybe not that big numbers because again calculators are not allowed so they they you know minimize in the work um that you do so you don't waste time again okay so in this question right here we have four five a what you simply do is a times one which is ten times one uh five you do five times sixteen and then two fifty six so you do four times two fifty six and then you just add all of them up and you'll get your tender value very simple so you simply just multiply it with the numbers i gave you 160 to 56 very simple how do you convert from daenery to um [Music] to hexadecimal you can divide by 16. okay the way for binary if you want to convert from uh dendrite to binary you can divide by two in the remainder on the side you can do the same thing for this but this time you divide by 16. or what you can do is just align 1 16 256 so on like that so that you can get your number unlike the method one what you can do if you don't understand again pause the video at any time you can read these notes and also down in the description i've been i've given you the notes so you can have a look at that too but again this should be quite simple so let's move on uh let's move on and now finally have a look at some uses of hexa decimal so uses of hexadecimal or some look at some uses of x decimal the first use is memory dumps okay and uh you you often you quite um sometimes you ask this question so it's important you know it so we have the first one memory dumps memory dumps is simply like a list of all numbers okay and um this happens you know to um you know memory simple memory okay it just means memory for example if i you know do something to a printer if i tell it to do something the memory stored will be stored in terms of hexadecimal in memory it's called memory but very rarely do you asked what memory dumps are so you know not a must to know that all you need to know is that a use of hexadecimal is a memory dump the next use is the html enough and you know i think you've heard of this uh quite often a very popular term that's used html hypertext language is also written in hexadecimal and this is not a programming language but it is a mock-up language and it's used for presentation and design i believe which is the same thing actually so it's basically used for the presentation of a website okay so presentation of a website and in this we have colors so part of hypertext markup language we have colors which is rgb and if you have noticed if you do um html if you know html you know these digits right here um this one ff00 you know that that is written in hexadecimal okay so you can see like this would represent red green blue and also so forth we then have media access control and uh this is is often you know asked so media access control is simply a unique address or a unique number that is used to identify a device on the internet the mac address refers to the network interface card which is the nic which is part of the device okay so the mac address is usually made up of 48 bits to about 64 bits and has about i believe um [Music] the first segment or the first half is for the manufacturer and the second half is for the serial number of the device okay so you can you know sometimes they ask you okay what is mac address so the moxie would get first four maybe it's four marks or three marks the first one you would say media access control already that will give you mark because you're simply saying that that's what it means media access control you can say it's a a unique number unique number that is used to identify a device you get another market you can then say that mac address is comprised of about 48 bits to 64 bits of hexadecimal digits get another mark then you can say first half for the manufacturer second half for the serial number another mark there so quite simple and um you do not need to know the types of mac addresses so uh types of mac addresses you do not need to know for the igcc levels um so we move on to that we move on to web addresses so we're about to simply uh all the characters they know keyboards they're assigned to something and we say this is called a cg code okay so therefore like the letter a on our keyboard has uh you know something in relation to a cg code okay for example right here saying a is uh you know in decimal 33 hexadecimal 21. sorry yeah so all of that okay so you don't need to understand what these numbers mean but you simply need to know a cg code is basically assigned to um a certain um hexadecimal value or it uses hexadecimal values to um you know sorry about that but we are back so what i was talking about is web address simply a cg code is assigned to um you know the keyboard or the letters and this uses hexadecimal values and simple terms okay that's all you need to know okay and um that's all for that and then of course we have a look at assembly code and machine code so assembly code is a machine code we'll have a look at that later in detail so basically this is um you know code that the computer understands okay and this uses hexadecimal and that's why we learned about binary and hexadecimals because it's part of the language of a computer and therefore we learn it okay so those are the users of um hexadecimal so we started with mac addresses um we had html in html we have rgb we have memory dumps we have the web addresses which uses the cg code we have the assembly code and the machine code okay so um i think that was all that we need to know okay was that all yeah that was all okay so those are the uses of hexadecimal you need to know them so you can revise them quickly we move on to chapter two communication and internet technologies again i made a video on most of these topics already but again you know um you can have a look at that so we're gonna have a look at communication and internet technology so basically what you learn in this chapter is um the different types of transmission rates we'll have a look at um [Music] you know we'll have a look at the checking error checking methods okay we need to know those we'll have a look at the web browsers and the isps and then finally we'll end with http and html so let's start with this now using computers have been a vital role in all our lives okay because we use computers in day-to-day basis and we send data from one place to another now computer science will help you by saying that you know this data is not always safe and it's very important to ensure that this data is not being changed while you send it to someone okay and therefore we come to this chapter where we're gonna have a look at how something is transmitted how we can check if there's an error and then of course have a look at you know safety stuff you know browsers do and isps do and then finally have a look at how to tell if something is secure how to tell if something is not secure okay using http and then html so let's start with data transmission and in dancer transmission we're going to be having a look at three factors the first one is the direction of data transmission we're going to have a look at the method of transmission and finally we're going to have a look at the method of synchronization between the two devices when you're sending data online so we're going to start with the direction of data transmission now data can be sent in many directions okay we have three directions that we'll be needing in the computer science syllabus the first one is simplex the second one is half duplex the third one is full duplex data transmission simplex data transmission is only in one direction which is from the sender to receive an end example would be from a computer to a printer the second one is the half duplex starter transmission which can be sent to both the devices over the both directions but not at the same time and you probably guess full duplex starter transmission is both the directions simultaneous again an example for half duplex transmission would be for example okay because a wakataki you cannot talk at the same time okay that's why they say over and out okay so that is a signal to say okay now you may speak okay so that is half to pick stock transmissions full duplex dollar transmission is like a call right now in the smartphones okay where that simply means that it's both directions simultaneously and can be sent from a to b or b to a an example b smartphones that we have these days okay then we move on and have a look at the different doctrinal transmission so that's quite simple we had to look at direction let's have a look at distance we're having a look at the distance of data transmission we have two types we have a serial data transmission and we have a parallel total transmission the first one serial transmission serial dot transmission is simply when data is sent one bit at a time over a single wire okay as simple as that so i'm going to highlight this it's a very good definition when data is sent one bit at a time over a single wire or chat okay as simple as that when they ask you what is serial dot transmission state that you get it correct okay i suppose that and this method of data transmission works well over long distances because again it's one bit at a time so the likelihood of it being unsynchronized when it arrives is very low and therefore usually it works very well over long distances but at the same time because it's only one bit at a time it's much slower than the parallel tertiary transmission when having a look at parallel data transmission this is when several bits of data are sent several are sent down several wires or channels at the same time okay several bits of data are sent down several wires or channels at the same time okay and this one would be a much faster data transmission rate but it can have a possibility that it becomes unsynchronized when it you know is sent okay so there we go we're done with that um and uh let's have a look at uh asynchronous and synchronous so now we're having a look at the type of synchronization okay so we've had to look at direction okay we've had to look at direction we've had a look at the type you know uh sorry we've had a look at the direction we've had a look at the type of data transmission and we have finally are going to now have a look at the type of synchronization so another look at the type of synchronization we have a synchronous and we have synchronous okay two types of data transmission rates so we start with asynchronous asynchronous data transmission simply basically means is that when data is being sent in an agreed bit pattern okay so asynchronous data transmission is when it's turned in an agreed bit pattern so this basically means that the data bits are grouped together and then are sent with control bits okay they're grouped together and then sent with control bits okay and um that is asynchronous data transmission with a asynchronous okay so agreed with pattern sent grouped together and sent with control bits okay and uh we do this so that you know when it's uh arrives at its destination it is not in separate groups but instead all as one okay then we have the synchronous start transmission synchronous double transmission is a continuous stream of data this data is accompanied with timing signals and an internal help which basically means that it ensure the sender and the receiver are synchronized with each other at all times okay so that's what the synchronous starter transmission does we now move on to the universal serial bus okay and we're learning about the universal serial bus because it is all you know related to the data transmissions that we just talked about the universal serial bus is asynchronous through transmission asynchronous remember is when it is sent in a grouped and an agreed bit pattern and is accompanied or is grouped together and is sent with control bits this is usb universal serial bus now very very low chances of you asking what the usb is made of uh very very low chances but it's good to know it's basically made of four wires two y is for power and the earth and if you do physics you would know this and two eyes for the darker side okay you know what power and earth is it's simply types of wires that are used in uh sort of components but what's the important part is the advantages and disadvantages here so here is the advantages and disadvantages table this is what you really need to know so devices plugged into the computer are automatically detected is the first advantage the second advantage is that it can only fit one way which prevents incorrect connections and it has become an industry standard which is means that every laptop will have a usb um sort of slot and um it should be you know accepted and then several different data transmission rates are supported so uh you know according to what device you have it will support that different type of data transmission rate it supports and then finally uh it is you know usually okay but with the disadvantages we have a maximum cable length of five meters uh it has a present transmission rate which is limited to less than 500 megabits per second so it has a slower transmission rate sometimes and the older usb standards may not be supported the near future like nowadays hardly do you ever see ethernet cables in laptops because everything of course is becoming wireless now it's not related but you know in the future there can be a possibility where we might not even have usb slots okay so where there can be a possibility where you know we're using no usb slots now let's have a look at the arrow checking methods finally error checking methods so error checking methods is simply a way to find if you know data has been corrupted as we sent it simple words okay and um simply we have a few types of you know error checking methods that we can have a look at the first one is called priority checking party checking is one method to use to check the weather if it's been changed not uh whether the data has been changed it's a very easy very very easy way to check now with body checking each bit is allocated a priority bit now before the transmission takes place basically what happens is that the sender and the receiver agree which party bit they will decide so for example the systems maybe they decide they will use even part that means that in the start they're going to count how many even parties uh so how many even numbers of one and then in the end they will also count how many even number of ones they are okay so that's how they look at it for example you have one one zero one one okay and this tells you which party bit are they using so what you simply do is add the ones one plus one plus one plus one is four four is an even number therefore it could be an even party bit okay very simple and it's usually often exam sometimes they even give you a blank and say fill in this blank to make it either even party or party very very easy questions these are three monks you have to simply just count the number of ones okay and uh you know if it's you want only four ones then you know put a zero or for example whatever you want to do for this example it says that you want to have even party that means the number of ones should be even so one one one plus one plus one plus one it's four yeah there are four ones which is even so you just add a zero but if you want auto party in this you have to add a one so that you can make it to five ones which is an odd number very very simple party bit is one of the most simple sometimes they also given these tables where you have to find you know the sort of missing party bit and then correct it very simple very easy and then what you have to say is like for example byte8 has incorrect party bit five as incorrect party you get your three months okay very simple very easy so this is all about parts a bit we move on to the next error checking method and the next error checking method is called automatic repeat request the arp the ar queue simply basically means it's another method to check uh whether the data has been corrected uh correctly transmitted so what it uses acknowledgments and timeouts that means that when i send a message it will use an acknowledgement which means that the data has been sent and has been received correctly okay and the timeout is basically the time allowed for you know the acknowledgement to be received okay that means that when i send data the timeout for example i put it five minutes if i don't get that acknowledgement then it will be set again okay so that's how it works very easy a or q the next one is checksum checksum basically is another way to check if the data has been changed or corrupted okay and uh checksum uh basically has a look and is sent in blocks of data and it uses an algorithm okay and this is the algorithm divide the sum x of the bytes by 256 so the first one for example of x i divide by 256 then i round the number to the nearest whole number so the nearest whole number um i would make that y so the nearest whole number if it's decimals then nearest whole number down okay so if it's 5.6 you do round down which will become five okay not seven and not six they become five then you do five times 256 and then you do the you know difference between the initial minus this and that will be your checksum but if it's less than 256 then it will just remain 256. okay uh so here it's saying that if it's greater than 255 that's the only time when you can do it okay that's the only time when this formula applies then we have echo check echo check simply is when data is sent to another device and this data is sent back again to the sender okay this basically means that the sender will compare the two sets of data and will then check if there's any errors that are occurred during the transmission process so basically you know confirming okay is the daughter that i sent in the start same as i got but these ones are very unreliable because you cannot identify which what error you know came so you can't you know correct the error because if it's two different data you don't know where the error occurred was it you know during the sending part or during you know finding it or was you know the error made when checking so we cannot tell uh where this is but it could check to simply as in it's called echo check you know check if whatever i was sent is the same thing as what i got finally let's have a look at internet technologies okay and here we have a look at isp ip address we have a look at ip addresses and mac addresses again we have a look at html and um yeah we then have to look at http and then web process okay so let's have a look at this now so um let's begin so we start with the um ip address okay so when having a look at the ip address uh sorry isp isp's internet service provider from its name as you guys can see isp is simply when um companies provide the user with access to the internet okay and therefore a monthly fee is usually charged this and basically these are companies that give you access to wi-fi or to the internet okay then we have the ip address the ip address is a unique address as the internet protocol address it's made up of 32-bit numbers and a home computer is given an ip address or the phone computer ip address and it is assigned by the isp which is internet service and is unique for each internet session then we need to know the difference between the ip address and the mac address now if you recall what mac addresses media access control unique number that identifies the device to the internet what's the difference now an ip address gives the location of a device but the mac address just identifies the device connected that's different ip address is the actual location of the device mac address is just the to identify we're having a look at html we've already have a look uh had a look at this but in html we have two main things that we need to have a look at first one is structure and presentation now html is not um you know programming language but instead is simply a mock-up language or simply um you know something that's used for presentation of a text on a web page so let's have a look at structure and presentation structure is the essential part of html document okay it has the meanings of stuff it has the structure of the document the presentation is the style of document you know like the font or something like that the style sheet okay that is the presentation okay so we have two types the um presentation and the structure then we have a look at the http hypertext transfer protocol http is basically some rules that must be obeyed when transferring files across the internet we'll have a look at some encryptions later on on how encryption is done during each website so we'll have a look at that we'll also have a look at certificates per website and all of that but what we is important here is that websites with https is secure for example youtube you will see https in the url that means that it is safe finally the last one is web browsers a web browser is simply a software which allows a user to display a web page on the computer screen it translates html code from website and shows the results they have a home page ability to store the favorites users web pages uses cookies we'll have a look at what cookies are and usually it's comprised with this http is the protocol used this right here is the web service name and this is the file name so you need to understand that okay so now we're gonna have a break because we have finished two chapters and then later on we're going to now have a look at the remaining six chapters and every two chapters will have a break so i'll see you in about um 10 minutes and um yeah so we'll see you in 10 minutes and have a look at logic gates and logic circuits okay so we just came a bit early and um we are back okay so finally we're gonna have a look at logic gates now so we're gonna have a look at some logic gates and talk about logic gates so we're gonna have a look at logic gates and of course the logic circuits now here are the um six logic gates that you need to know that will be asked in igcc the first one is the not gate the not gated triangle with the circle the and gate the nand gate the or gate the nor gate and the zor these are the six gates that you need to know okay now two tables um is simply uh usually what you're given is for example you're given a circuit and you're told to find the output okay that's what we're going to be learning in today's video but before having a look at that we're going to have a look at the functions of the logic gate of course so we start with the notch gate the not gate looks like this and basically it has only two inputs okay so it has only two inputs either it can be zero or it can be one sorry it only has one input sorry it only has one input it can be the zero or one and what this does is basically it's the opposite okay it's the opposite in the boolean algebra we say a and then a line on top okay line on top is a then when you want to say the logic notation we say not a okay not a then we have the and the gate the and gate looks like this and you have to simply you know um okay uh so what you have to do for the and gate is you have to multiply okay so zero times zero zero zero times one is zero one times zero is zero and then one times one is one for the nand gate it will be the opposite the or gate it will be addition so zero plus zero is zero zero plus one is one so fourth the nor gate will be the opposite so example i've talked about the nine gauge it's the opposite of and gate uh nor gate opposite of or gate and then finally the zor gate simply says that whenever you have the same terms like one and one then it could be zero but when you have different terms there will be one output okay so that's simply what you have to do okay and what you simply do is usually whenever you're given a logic circuit you have to label each part with a certain number for example you have maybe label this p yeah you have to label this q label is r and then label this s okay then what you simply do is this example right here is in uh and gates okay you know this is a navigating and i can show you right here this is an and um if i go back to the and gate uh right here this is an and gate okay this is an and gate so let's identify all the gates here this is the and gate this right here is the nor gate okay remember the the not gate is the triangle the nor gate is you know a bit of a turn there like that okay and then every time there's a circle it means the opposite of the actual one this one is the or gate this one is the zoho gate because that has two lines after you get to know that you simply have to split the table okay for example right here the input values uh you split the table and using the input values okay because you know for example in this one the value of a and b is entering into the and gate okay and uh you can see a and b so and gate remember you have to multiply so zero times zero is zero zero times zero is zero zero times one zero all so forth except one times one is one one okay and that's how you get the answer now logic circuits logic gates um you know it's quite hard to explain it like this but instead you should best do it with practice so i advise you to you know do some questions and then look at the marketing scheme if you're correct but simply what i just said was the basic of logic kit circuits i cannot you know explain more about this this is more of a thing that you have to do more practical and not uh you know theory so practice on the gates and you should be okay and you can already see you know it's a small chapter related to these circuits so these are just some examples do these examples i won't be doing them right here because it's quite hard to you know draw them but you know hopefully you understand this so we're going to skip over to chapter four where we talk about the operating systems and the computer systems okay so operating systems and the computer system so let's have a look at this now okay so we're having a look at operating systems and computer architecture okay we're having a look at um all of this okay now uh operating system is simply a software that runs in the background whenever you're using a computer system okay so whenever you're using a computer system we use or we need operating systems okay so in this case what you need to know first of all is some uses of the operating system okay so for example one error handling two batch processing uh you know i'm just you can you can pick any from these okay any from these would be correct anything from here would be correct as you guys can see anything from here would be correct okay so hopefully that you have understood um and hopefully you have got that okay so those are just some uses that you need to know uh this one i cannot you know explain this you just need to know the uses of the operating system and um i can't do that but instead you have to learn it yourself okay um i cannot help you in memorizing the following okay so hopefully you have understood that um and you've got or understood that okay we move on now okay we move on and now let's have a look at interrupts and a buffer okay so operating system remember is a basically a software that runs in the background whenever you're using the computer so let's have a look at what an interrupt is an interrupt is a single uh signal sorry sent from a device or from the software to the processor an interrupt is a signal that is sent from a device sorry very sorry about that but we move on we continue so interrupts and buffers so interrupts what i was saying is it was a signal that is sent from the device to the processor now you'd ask yourself why do we need an interpol what's the signal about now the signal is simply um assigned to tell that you need to stop whatever you do it tells the processor stop whatever you're doing and help in simple terms okay so an example would be for example you're printing something and the printer says that it has a paper jam an interrupt will come up a signal will come up and then it will send to the processor okay and then once when the interrupt signal is received the processor can either carry on with what it does or it will stop and service the program that's simply what an interrupt does its signal sent to the um software to or to the processor or from the software to the process to stop whatever it's doing and focus on what you know it needs help then we have buffers which are used in computers as a temporary memory area okay so basically the buffers are used in the computers as a temporary memory area okay this basically means that these hardware devices operate at much slower speeds okay what that basically means that for example i'm streaming right now buffers basically help the computer that you're watching this device on to know ahead of time okay to know ahead of time so therefore there won't be any buffers as its name comes no buffers there won't be any stops um and therefore you know there'll be a smooth run of entire or everything okay so that's why we use buffer so that's why we need buffers okay and uh that is the importance of a buffer okay so we move on now and um we have a look at okay these are some examples that are given by the notes uh some examples of you know when you would need a buffer but a good example would be when you you know you have the video that is the um best example that i can give you okay so uh let's move on now let's have a look at computer architecture okay so that was just about computer systems is quite small topic about computer systems but now we have computer architecture it's a big topic computer architecture okay computer architecture what is computer architecture now computer architecture from its name is simply what a computer is made up of okay what is you know it's made up of okay simple times now a computer uh system or the stored program computer we say something called the von neumann architecture okay so a common term that's usually referred is called the von neumann architecture and this is a concept that was invented by john von neumann and this basically was an idea of the stored program computer okay and his idea was that you know to hold programs and data in memory okay so you basically hold the programs for future use and we use something called the font human architecture for this now the one human architecture has a diagram here is the diagram that we're going to have a look at here is the diagram hopefully you can see so the diagram basically starts with the processor which includes the control unit okay so we have the processor which includes the control unit we have the memory unit input and output and then we have the um hello device and the yellow device now we have three types of buses that you will come across we have the address bus the data bus and the control bus okay these three types of buses okay so here's a table that is explaining each three type of bus okay um but uh yeah so we have the address data bus and control bus okay so the address bus will carry signals relating to addresses okay so it carries signals related to addresses okay and it's unidirectional the data bus sends data between the processor and the memory unit and the input and output devices so it stands the data between the processor the memory unit and the input output devices and is by direction the control bus will carry signals relating to the control and coordination of all these activities within the computer which is unique direction so control bus deals with all the signals relating to the control and coordination of all activities data bus is data between the processor address bar sky signals relating to addresses those are the functions of each here we have a diagram again of um another sort of thing that you need okay so yeah that is that and now let's have a look at how everything works okay how does this work now an address is the location of where the data can be fought okay and uh you need to know how everything works and i believe i think you you you will learn it in the fetch execute cycle in just a moment so we have the memory units in the memory units it's basically the number of partitions um in each partition consists of an address and its contents um this is very rarely asked but you need to know this the mdr mar is the memory address register the mdr is the memory doctor register alu's automatic and logic unit pc is the program counter cir is the current construction register okay so um here we just have some examples of how they looked at and then here we are told what a processor is what our control unit is and what input and output devices are so processor basically contains the arithmetic and logic unit okay and the alu allows our thematic and logic operations basically this is calculations the control unit operates um the memory okay processes the input and output devices and it also contains the cir and the pc you have a look at what you know each function does in just in the fetch execute cycle that we're gonna have a look at input and output devices we have been seeing this you know since you know everywhere input and output devices very common in these exams uh we have so many input and output devices printers monitors lots because we all know what this basically means um so shouldn't be okay so what is the fetch execute cycle such execute cycle is basically used to uh carry out some instructions the processor first of all fetches data and instruction and then from the memory and store them in a suitable register okay so here is how the fetch executive cycle works in the fetch execute cycle the next instruction is fetched from the memory address currently stored in the pc so instructions are then fetched from the pc they are then stored in the cir and the pc is then incremented or increased by one so that the next instruction can be processed execute simply basically means that the processor passes the decoded instruction as a set of control signals now i have made a video on this but this is the main table that you need okay this table right here that i'm going to show you here is what you need to understand the first one the program control the pc contains the address of the memory location for the next instruction to be fetched the address is then copied from the pc to the memory address the mar and is done by the address bus so the pc to the memory address register so the pc remover contains the address of the memory location of the next instruction which has to be fetched okay then the pc uh the address is then copied from the pc to the mar with the address bus from the mar it is complete temporarily to the mdr okay and then from the mdr it is converted to the cir okay and then finally again if you want to see which buses you know do the following uh sort of stuff uh let's have a look at this okay so the first one you remember i told you it was um this one is done by the address bus this one is done by the um is it one second this one is done by the doctor box the second one is done by the data bus so let me go there back so the second one so let me do it right here so this one is address plus so we have three address bus then we have the um one second we have the data bus so i'll just write that up data bus so we have the data bus and then we have the control bus from here and here we have the address bus okay these are the buses that are used to you know convert the stuff so the first one is the address bus the second one is the data bus third one is the control bus okay those are the ones that you need to understand or you need to know okay so hopefully you have got to know what this basically does what it basically means you can have a read on this you can pause the video and see what you know what's happening everything that's happening and um what is being done okay so that is that hopefully you have understood this and the next chapter we're gonna have a look at is input and output devices okay and um that will be the next one you can see the how many input and output devices are so we're going to quickly go over all of them so let's move over and do that so again we'll take a 10 minute break like the other one okay so finally now let's have a look at the input and output devices um so yeah we're going to be having a look at input devices now this is one of the longest chapters as you can see all the input and app devices it's so long so let's see how long this is going to take um this is chapter five so we have three more chapters of this um so let's have a see uh let's have a look at this now so i think the next chapter what's the next chapter let's have a look at the next chapter uh the next chapter is on you see it's you see how long it is very long the next chapter would be so long still still continue still continuing still continuing wow still continuing so it's still continuing this one is taking us a long time then the next one is about data storage um yeah so dot storage and then we will conclude or not then it's chapter seven i believe then we're gonna have a look at high and low level languages and then the next one is um errors and then we're not gonna be doing practicals remember because you're only going to do theory okay so let's start input and output devices long talk big topic very like robotic 60 pages okay input output devices let's begin let's see what we can do um so now input devices that you need to know and these are the upper devices so here's the input devices you need to know these are the output devices you need to know so let's have a look at each of them of course we're going to be looking at each of them step by step like you know what scanners are interactive white codes all that so on so forth now scanner um we have scanners parkour readers quick response digital cameras keyboards pointing devices microphones touch screen sensors interactive whiteboards then we have um inkjet printers laser printers 3d printers 2d 3d cutters actuated flat speakers lcd led and then projector so we're gonna have a look at all of these individually and how they work so that's why it's that long and then again we're gonna have a look at some further you know inside stuff like led you know how they work difference between lcd led and so on so forth let's start with the input devices to start with scanners now scanner is a 2d or 3d um two-dimensional or 3d uh hopefully you know what that means um now today i'm sure two dimensional scanners sorry are basically these are types of scanners that are usually uh used or the common ones that are used um and what this one is is basically uh this is the one where it's simply the image is converted into an electronic form and can be stored in a computer so this one is stored under the commute computer as it is converted to the electronic form okay so this is how you use the scanner and uh you know nowadays everyone use knows how to use the scan actually so what happens is a basically a bright light illuminates the document and it's converted into electronic form and then it can be stored onto computer that's how this kind of works a three-dimensional scanner is a bit different because this one scans solid objects because of course it's 3d and what it ha does is that it takes different images of the points and then it comes up with one um you know 3d dimensionals canon you know usually for like projects when uh we're having a look at buildings we use 3d scanners so what are some applications of scanners so the first one um would be 2d scanners are used at airports to read passports and they can also be used um for ocr technology which is basically uh digital images which represent the passport pages because the ocr technology um is of course used okay so basically um we don't need to know a lot about this but basically you know whenever in the airport we go in the airport they usually ask you for you know some form of um uh you know face id for example so we use the scanners for this we use scanners to identify following okay so for example right here it's saying um you can use the distance between the eyes with and the nose the shape cheekbones everything it's done by scanners 3d scanners to be more specific um sorry 2d scanners but 3d scanners can be used again for x-rays for buildings you know as i was telling you before so that you can see how it will look in real life and um yeah so scanners are really important but um usually all levels i believe they don't even ask you that much detail but instead you only need to know um the fact that scanner simply converts some object to an electronic form which can be stored onto the computer that's what you need to know like mainly uh then we have a look at barcode readers or barcode scanners and uh basically what this basically means uh is that a barcode a uses or reads okay so this is a very interesting um input device so what happens is that in your barcodes um they're comprised with different lines parallel lines um with different thickness so what the barcode does is that when you scan it what it'll do is it'll see um you know depending on the width the intensity meaning if it's darker lighter it will scan that and then it will come up with you know the information that it needs it's usually used for you know shopping markets or something like that so this is an example of a barcode as you guys can see right here and when you put the barcode on top of it it will measure the thickness of the lines the white parts the dark parts you know thin parts and everything and that's how it comes up with stuff now you don't need to know all this um never asked rarely asked so you never need to know you don't need to know about now our barcode is first read by um led then the light is reflected back off the barcode and then the reflected light is read by the sensors then after that the uh led light is scanned across the barcode and it's converted to digital data okay it's kind of or electric electronic form but it's simply converted into a certain data type of data okay so that's how it works okay it's a quite simple way now it works um and uh yeah very quite simple wait um now let's move on and um let's further talk about this okay so now um let's further develop uh this now what it basically says that um input and upper device and how it's used so here we have uh some you know examples of each of them or some examples of some input devices and what we have to do is tell you how it is used okay so the first one keypad okay keypad is basically to key in the number of the same items and we have the monitor which is used to see the cost we have the speaker which can you know make a beeping sound every time the code has been read we have the printer which will print the receipt we have the magnetic strip reader and then we have the touch screen so you know whenever you go to like a shop uh whatever you see is probably what you need to know or get to know okay so it's quite simple and uh quite very you know easy to understand i would say so there shouldn't be any difficulty in this so let's move on um let's talk more about parkour readers so okay so how so the barcode has been read what happens then so what you can say sometimes they can ask you how does you know the whole procedure of stock work so basically what you can say is that um you can have the database the stockpot space having a key field for each stock so when the barcode number is found the stock item will be looked up then the reduce once when it is paid for it will be reduced by one then the new value of the number stock is written back to the stock item record so this is more of general uh knowledge so it shouldn't be a problem actually it's uh more of general knowledge um for um this part of you know the question so um that is that um we can have a look at advantages so you know in advantages it's easier faster you know no need to price every stock item you can automatically detect allows automatic stock control and with the advantages of using a barcodes to the customer would be that you know faucet checkout so you don't have to waste time um also you know cost savings can be passed on the customer there will be fewer errors so you know that's that let's have a look at qr codes quick response and this is another type of barcode and it's made up of matrix the other one was made up of parallel lines this one is made up of matrix filled in dark squares works the same as the barcode reader that's why you know it doesn't i'm sure a lot about this uh but it's basically made up of matrix squares then we have the digital cameras so a digital camera is simply um used as a traditional camera to you know record photos the film required developing and then printing before the photographer can use now in the olden times you know there was nothing like this you know they had to do the old primitive way the hard way um and now you know technology is improved by a lot so everything is becoming really easy so digital cameras being one of them where it basically records photos and videos and cameras can now be controlled by microprocessors it can adjust shutter speed focus on image automatically i just aperture size adjust size of the image and there's a lot that i can do let me come over to keyboards i'm skipping some stuff because you know it's usually not relevant in the idc's exams never asked so that's why i'm just you know skipping through it because right now we are focusing on only things that will come on the idcc exam but again at your free time if you want to read this again the notes are down in the description so you can have a look at that so keyboards let's have a look at what a keyboard is keyboard is the most common um input device that is used for data entry and uh basically input device on computers tablets mobile phones and other electronic items and of course there is also the keyboard that is um classified touch screen technology so we also come back as a keyboard okay the ones that are on your mobile phones it's still a keyboard okay and we have something called the ergonomic keyboards which basically are for people that have rsi in the hands so if you use uh rsi is basically repetitive strain injury what it basically means that when you use the computer a lot sometimes you can have some errors or something sorry you can have some problems that can occur and therefore we have a special keyboard made for that it's called the ergonomic keyboard or sometimes they say for disabled people okay and um yeah so that is that hopefully you understand keyboards uh when having a look at pointing devices we have um a mouse which uses a tracker ball okay uses uh that trackball right here okay so for example like right now in this live stream um i'm using a mouse this is a mouse uh if you can see right here and uh you didn't notice behind the mouse uh this right here is basically infrared sensor so wherever i'm moving it on my table it will detect the movement and accordingly it will move my cursor or mouse so that's how a mouse works so it detects the infrared will detect uh what happens and then monitor the sort of you know movement i'm making with my hand or with the thing and then of course it has the racquetball uh which you can see right here it has the jackal ball too and then the left right okay simple mouse um but hopefully gets the job done uh let's have a look at microphones uh microphone is an input device okay and um it's used for voiceovers uh right now i'm using a microphone voiceovers to talk over the stream um and so on so both and uh microphones are usually now built into laptops computers um phones um you know all electronic devices usually have a microphone so it's become more of a you know standard use and um most devices have microphones but in all times you have to you know separately by the microphone and then connect it to your external device um the way you know nowadays uh you have a monitor and you separately attach it to the pc but of course now you know technology has improved a lot uh here we have some you know irrelevant stuff about some speech recognition and so on so forth stuff like that um when having a look now finally let's have a look at touch screens okay so we have i believe three types okay we have the capacitive we have the infrared and we have the resistive okay we have those two capacitive infrared and resistive so let's have a look at the first one capacitive top screen so a capacitive touch screen is made up of many layers and um so here is the key with many layers it's made up of many layers of gloss that acts like a capacitor that creates electric fields between the gloss plates and layers so it's many layers that creates electric field which detects you know movement on your hand when the top gloss layer is touched the electric current changes and this will therefore locate the coordinates of where the screen was touched okay so the electric current will change and that's how it's identified the benefits of this is that it's a medium cost technology uh the screen visibility is quite good um in strong sunlight of course uh it permits multi-touch capability because again you know when it detects to um change in currents it can be a bit you know good and uh quite good or capable of doing that the screen is very durable and will take a major impact to break the glass the drawbacks is that it allows only the use of bare fingers and not the use of um [Music] gloves for example if you're using glass because with use of gloves it will not detect that electric current okay infrared infrared is um heat sensitive and they're optical they're two types heat sensitive uses glosses uh optical also uses glosses both of them are the same but with the difference is heat sensitive needs a warm object like fingers but optical it uses anything okay it can be um you know wherever whatever is touched on the screen it will be using a grid coordinate um system to locate where or what um part of the screen is touched the benefits of this is that both systems allow multi-touch capabilities basically i can click two things at the same time and it will detect also the optical system will allow the use um of bare fingers gloved fingers or stylus so you can use a stylus you can also use gloves and um they have good screen durability so you can see durability is in all three i think um except the last one the drawbacks is that um it's relatively expensive uh heat sensitive system uh only allows spare fingers because again you know you need something warm and um both systems have very good screen visibility and strong sunlight okay which i don't know why isn't the drawbacks i think it's the problem with the notes because um okay resistive the last one um this makes use of an upper layer of polyester so it's a type of plastic and it's basically again layers so if you notice most of them are layers even the previous one was a layer um yeah so most of them are usually layers um and this one is made up of polystyrene and the top polished bottom polister is basically completes the circuit the benefits let's move on there um it is relatively inexpensive uh and so the only thing that's expensive is the infrared i believe yeah that's the only one that's expensive um the other one's resistive but not expensive you can use bare hands on gloves and then drawbacks is that screen visibility is poor and it does not permit multi-touch capability let's move on to sensors um so with sensors is a very important but uh let's have a look at each sensor um individually so we start with temperature temperature can be used to control heating systems monitor chemical process uh monitor temperature anything related to temperature is used to temperature sensor the next one is moisture okay so we have temperature that we did so uh control heating system chemical process greenhouse okay so this is everything related to temperature whenever you've got moisture you can have to control monitor the moisture levels of the soil okay moisture levels humidity levels um dampness so usually it relates to something in the greenhouse or the factory then we have light uh you know switching on the light on and off monitoring car control um levels automatically switch on the car's headlights when it gets dark then we have infrared um so you understand that okay infrared is you know for example turn on wind screen wipers automatically uh detect intruders buggler alarm count people entering leaving building pressure anything related to pressures then we have sound we have gas with ph so you can see how many we have we have many so you can um you need to know these ones okay so let's move on so here's just some um some more examples related to that so yeah so here um what these questions are is simply the use of a microprocessor okay and this was a new um segment that's usually asked and um i think i predict that next year this question will come according to my predictions this question may come uh this one is more of um knowing your computer science and all um you can't just teach it you need to know how a microprocessor works and the sensors that it needs and um this one i can't really explain right now but hopefully maybe a future video i can have a look at many examples and teach you how to sort of do it okay so let's move on to output devices so on our device we start with inc inkjet printers now in inkjet printers is usually made up of spread operators so it sprays droplets and then you know print something uh it has an ink cartridge or cartridges so it uses ink cartridges or cartridges uh which of course which is for each color a blue yellow magenta and of course the black cathode so if you see in your printer those four colors uh if you have an inkjet printer nowadays it's usually um used in many forms so you should have a printer it has a stepper motor which moves the printhead so that it can spray the droplets and then of course the paper needs to be feed by you not automatically so here is some process of how you know um the inkjet printer works so data sent to the printer so this is general knowledge data sent to the printer print ensure the format is okay checks if the printer is made and sure the data is then sent to the printer and temporary memory known as printer buffer we have talked about printer buffer um a sheet of paper is then fed into the main body it goes over the body prints the things by spraying the droplets uh each full part of the print head advancely very slightly to allow the next line to be printed so it moves next line line by line then if there's more data in the print profit it will repeat the stages and then finally once when the printer buffer is empty it will release the paper so that's how an inkjet printer works let's have a look at the laser printer laser printer says that laser printers differ greatly from inkjet printers the way they print pages so they use a dry powdered ink they use a dried powder ink rather than liquid ink and they make use of properties of static electricity to produce the text and images okay so yeah laser printers this is how they work simply but this one uses a drum drum that rotates um so similar to the inkjet except this one uses the drum rotates and the toner it uses toner so yeah applications of inkjet and laser inkjet is best for one of photos while laser is good for high quality printouts then we have 3d printers 3d printers is simply used to print three dimensional objects the other ones were 2d this one is 3d and it uses materials um and it's made layer by layer and uh yeah so this is more you know straightforward so what it does it's used with a blueprint so we say cad software uh then it's sent to the printer the printer will then you know you have to choose the material it will print with the material and the solid object is built up layer by layer and then it can take a long time usually several hours depending on the thickness of the layers that you use in the material that you use you can also use uh 3d printers to cut stuff not only to print stuff but to cut stuff because if you replace the the you know the part where it prints to a cutting object it will cut stuff for you so it'll carve stuff for you use this for 3d printers uh general knowledge i be i believe it's quite general knowledge like um you have um fashion art technology you know parts in aerospace because you know they need to be precise anything that needs to be precise will be needed 3d printed so actuators um will be talked about later but simply they're used to control applications um loudspeakers headphones you can see how long this topic is very very long okay this topic is this is along very long topic so last speakers headphones um baby to the uh data from digital to analog and as you can see the diagram right here from dac to amplifier uh we move on to lcd led again i'm skipping some stuff but again you can read that all but because some of this is unnecessary like um you don't need to know the rate at which the dse translates okay so um you know you don't need it okay so lcd led wow uh very long topic um lcd led then oled projectors wow very very long topic but i will do it in this live stream as you can see this lesson is very long because we're covering all the topics that can never be found computer science so um lcd led um so here we have the liquid crystal display lcd technology uh that's the full form liquid crystal display and it's used in televisions these days so basically it's made up of layers um so yeah now when having a look at some characteristics of leds they are more popular because of the advantages you know uh one of the advantages is because maximum brightness uh whiter light uh brighter light um they lost almost in definitely okay as you can see nowadays even some old computer sorry old um televisions they still have lady that are even like 20 years old and leds consume a little power that's why you would use it over lcds as these are old oled is the new ones oleds are brighter light than ldds they don't need backlighting like lcds and they're modern okay when having a look at the projectors um basically a projector uh uses something called the dlc chip the dlf dlp chip which is the digital light projector um so digital light projectors dlp chip okay that's what's called digital light projector so basically um we use mirrors too and then projects on the screen we know how projectors work um lcd projectors are older technology than dlp but it's the same thing so it sends a powerful beam of white light from the bulb or led inside the projector body and then this beam of light is sent to the group of chromatic coated members okay so that's how it works and finally now chapter six okay chapter six um here we are gonna have a look at memory and data storage okay so let's have a look at memory and data so again we're going to be having a 10 minute break and then have a look at this memory and data storages [Music] what's up guys welcome back to another this computer science video today we're going to be looking at the memory and storages so today we're going to cover the entire chapter related to memory and data storage so further do let's begin so in today's video we're going to be looking at the different file formats such as the midi the mp3 the jpeg we'll also be looking at the file compression techniques we're then going to be looking at primary secondary offline storage and finally we're going to end with magnetic optical and solid state media so let's have a look at the introduction so basically there are many file formats used to store data and you know it can be either text it can be image it can be sound um so we have different sort of types of formats okay and in this chapter or in this video we will be considering how file compression is used to save memory into your computer so these computer systems have primary memory secondary memory and the main technologies used are the magnetic optical and solid state these are basically storage devices the magnetic storage device optical storage device and the solid state storage devices okay and they all use technologies that is going to be described in today's video so let's begin first of all is file formats okay we're going to look at the different file formats uh so as you guys can see there's the list right here we have the midi we have the mp3 the mp4 the jpeg and the text in number format so we're going to start with midi so the full form of midi is musical instrument digital interface so musical intege musical instrument digital interface the midi so what is this so this is basically a storage device for music okay specifically specifically for music it just comes from its name musical instrument digital interface it stores music files however the mitf files are not music and don't contain any sound so it is usually thought that it stores music but it's actually not so that's uh something uh cool to know but the mitf files are not music and do not contain any sounds they are very different for example the mt3 files okay so the mp3 files can store music or sound but this is not like that the midi is essentially a communications protocol that allows electronic musical instruments to interact with each other so it's a communications protocol that allows electronic musical instruments to interact with each other the midi protocol uses an 8-bit serial transmission and we have learned silver transmission in the previous videos uh basically serial transmission is in one direction one bit at a time uh with one start bit and one stop bit and therefore it is asynchronous we have also looked at a synchronous um in this you know in the videos that i've been posting on computer science an midi file consists of a list of commands that instruct the device okay on how to produce a particular sound music note okay so it's all related to music and therefore it comes it's not like stores music or anything but deals with the sound of music okay so that's essentially what's done there uh next up is that the first byte is the status byte uh so how does the midi work so the first byte that is sent or is the status byte and this basically informs the midi device what function to perform then after that encoded in the status byte is the midi channel and the miti operates on 16 different channels which are numbered from zero to 15. okay so let's look at some examples of the miti okay the midi commands would be note on and off okay this indicates that the key has been pressed to release like that would be for like an electronic keyboard you can tell that once when i've pressed you know it will be either uh it's on or off okay then it looks like key pressure with the key pressure it indicates how hard the key has been pressed and you know this could indicate the loudness of the music note then additionally the bytes are required of pitch byte and then we have the velocity byte which shows the device how loud to play the note so basically when the music note is played or when the sound is recorded on a computer system the midi messages are saved in a file which are organized by the file extension the mid dot okay so this is the file extension the midi okay mid sorry dot so the dot mid file is played back to the musical instrument such as an electronic keyboard okay the music will be played back in an identical way to the original so basically the midi is simply just how it can play electronic music okay it basically processes and then sends the audio back and therefore the whole musical note is set and it can store the entire piece of the music whatever you play maybe from a keyboard it will store everything depending on the pressure depending on you know all the the top things mentioned if you have pressed a note or not it will record that and that's where mitf files are and then the midfields are stored on the dot mid so that's a lot about midi and it's pretty very important apparently ngcc it's a little off topic uh to computers but it is midi um and simply the midi helps or allows electronic music instruments to interact with each other so in simple terms in midi is um something that allows an electronic musical instrument to interact with each other so now we move on to something that's really popular the mpeg-3 and the mpeg-4 we usually always encounter this uh when we are um you know looking at files or when we're downloading something it's always mp4 mp3 we also have the device the mp3 player so what is this mp3 what is this mp4 you know what is it all related to so the let's start with the mp3 okay the mp3 uses technology known as the audio compression okay to audio compression to convert the music and other sounds into the mp3 file format okay so essentially this compression technology will reduce the size of a normal music by 90 so this is where compression also takes part and also in igcc you need to know about compression and we will talk about that in future videos so basically compression is taken place and it reduces all the way to 90 percent okay for example an 80 megabyte music cd can be reduced to eight megabytes okay so it is compressing without anything getting lost okay so the mp3 files are basically used in mp3 players computers or mobile phones and these files can be downloaded from the internet or cds can be converted to the mp3 format but how can the original music file be reduced by 90 while still retaining its music quality so this is done by the file compression algorithms which use phariseful for periscope music shaping which is basically essentially that removes sounds that the human ear can't the human ear can't hear properly okay so that's just a brief uh you know way on how compression works basically some sounds are not heard for are not heard by humans okay um in physics if you've done it you know that humans gone here below 20 uh below 20 hertz and more than 20 000 heads so in the mp3 things that are below 20 hertz it will compress and therefore it will make a difference for the human ear and uh still keeping its quality and reducing it um sort of it's removed it's it's removing its uh what do you say the size yeah remove the size okay so these mp3 files use what is known as a lossy format since part of the original file is lost losing the compression algorithm so basically the mp3 files are um what it happens is that the lossy format okay the mp3 files use what is known as the lossy format okay basically the format is reducing the compression and then what format it is right now currently in that becomes the lossy format so also keeping that in mind you know we have now the mp3 so mp3 is basically compressed and then we have got that now we move on to the mp4 the mp4 is a bit different that before stores video okay not uh it does not okay it also stores music uh it stores a lot actually the mp4 is stores music videos photos animation but usually it's for videos along with audio and uh videos could be streamed from the internet using the mp4 format without using any without losing any real discernible quality we then finally come to jpeg files jpeg files are very important with images or not important but very common in use with images the resolution of the photographs is reduced from a to e for example okay from a such a resolution it can go to resolution like this okay and this reducing uh the pixel resolutions okay the number of pixels are reducing okay and that's how we come to this okay next up we have the uh sort of formats you can have a bmp image you can have a tif image you can have a bmp image so on so then we move on to some text and number file formats okay we have the cg format that we looked uh in chapter one you can watch that video i did talk about a brief a ct format and how it uses hexadecimal okay so hexadecimal is used in the cc format basically you can check that video in the end i talk about users of hexadecimal ending that a cg format comes into play so here we just talk about more about the text number five formats you know uh so on so forth but we talked about los less and lossy compression and i was actually not aware that it was going to be in the same chapter but let's have a look at this the lossy less and the lossy file compressions so with the lossy file compressions basically the data bits from its original data are reconstructed okay when the file is again uncompressed this is particularly important so basically lossy file compression is when it is compressed from the original file okay and then the file is again uncompressed okay we look at we look at this more in detail basically uh with lossy file compression velocity file uh with lossy less and lossy uh you just need to know the meanings of it and that's i think the most popular most uh important sorry not most popular but you just need to understand about that so with the lossy file compression we you need to know that mp3 and jpeg formats are examples of that and now with lossy less it could be like a spreadsheet file okay so there it is we looked at all the compression okay so um yeah so that was basically a video that i made some time ago displayed it on live stream and we're going to continue from there and we're going to have a look at memory and storage from there so uh when having a look at memory storage we have three types we have the primary memory the secondary memory and the offline memory it's actually a quite big topic uh where we cover primary secondary and offline storage okay so let's start with this uh let's start with primary memory then move on to secondary memory and then finally end on with offline so we start with primary memory so when having a look at primary memory we're having a look at ram and rom okay ram rom um as the primary memories mainly okay so what is ram so ram is the random axis memory okay and this one is temporary okay it's a volatile as okay this basically means that when the contents of the memory are lost due to power maybe you cannot um you know retrieve it because it's temporary okay and um it's usually used to store data files and um parts of the operating systems that are currently in use okay that are currently in use now it can be written um to a red from and contents of the memory can't be changed okay so that's ram um and then we have the dynamic correct okay the dram okay and this basically means it's a number of transistors um that have tiny uh single ram chips that contain millions of transistors and capacitors so um usually in this igcc um exam you only need to know around rome you don't need to do no drops so i'm just going to skip that for now so when having a look at rome okay rome is read only memory that one was random access memory this one's in read-only memory this one is non-volatile that means it's permanent okay so read-only memory is permanent random access memory is temporary temporary is the same thing as volatile and um permanent is non volatile okay and it's usually used to store important documents um so that you know in case power is lost you can retrieve it and um because it's only read only memory it cannot be changed that one can be changed i believe yeah so when having a look at the application of the two the rom is used to store factory settings um remote control frequencies um you know startup routines um set routines and stuff like that stuff that i use on a daily basis uh ram though uh sorry the rom sorry balance um because you know you don't need to edit anything because you know it's the same process again and again but for ram uh you have its own routines new instructions um and can be used to you know received and send uh instructions so now let's have a look at secondary storage and here we have a look at hdd ssd uh we look at uh yeah we look at those two ssd and hdd so let's have a look at this too so let's start with hdd hdd is um simply the most common method to use uh to store data on a computer okay so data is stored in a digital format uh on the magnetic surfaces of the disk okay so data is stored on the magnetic surfaces of the disk which is called um platters okay and the hardest drive will have a number of platters which spin about 7 000 times a second very quickly it spins and the number of uh red right heads can access all the surface and they are described so basically the data is stored on the magnetic surfaces and the hdd has magnetic surfaces so sometimes in igcse questions they can tell you to differentiate between hd and ssd sdd sorry so you need to know the folder okay so um then we have a look at normally each platter will have too quickly typically they can move from center of the disk to the edge of the disk and then back again 50 seconds um then we have ssd ssd is solid state drive and they have no moving parts actually has moving parts uh this one has no moving parts does not rely on magnetic properties and uh yeah so on so forth uh you do not need to know ee prom um so i'm gonna skip that okay so um so what is the main benefits of using ssd rather than hd so here's the summary um they are more reliable because it has no moving parts ssds are more reliable uh they are lighter um which makes them suitable for laptops um they have um they don't get up to speed until they work properly so they you know once when they work properly they get up to speed uh they have low power consumption um no moving parts therefore they're thin um and it's data can be accessed much quicker than hdd when having a look at offline storages we're having a look at cds dvds blu-rays i believe dvd ram um so on so forth like that so let's have a look at that right now so um cds and dvds so when having a look at cds and dvds we're having these are basically optical storage devices and they use laser light to read the data while blu-ray uses blue light you'll see that right now so it's basically a spiral track uh general knowledge you should know this um so it uses red laser okay um that's mainly what you need to know dvd ram um it uses a different technology to see these and dvds but basically what they do is instead of a single spiral track they use concentric tracks okay that's the difference and um this allows them to simultaneously read and write operations to take place blu-ray as i said um blu-rays uh use uh blue laser rather than red days compared to dvds okay so that's that um here is the quick sum summary between the two so cds red laser dvds red laser blu-ray blue laser uh you don't need to know the wavelength um but if they ask you one good uh blu-ray has the smallest wavelength see these are the biggest one uh and yeah so that's that okay uh flash memories usb flash memories uh basically it's a solid state technology ssd so it's lightweight portable uh you know general knowledge that's what we usually don't talk about this um yeah so we're gonna skip this because it's all lost okay and now we then move over to high and low level language so i don't think this is a very big topic because we only have two new know three parts um and this is the table that you need to know okay so this is the best table that you need to know for this entire topic so compiler will translate a high-level language to machine code interpreter will execute a high-level language one statement at a time like python assembler will translate low-level language to machine code so compiler and assembler both to machine code but compile a high level language to machine code assemble at low level language to machine code compiler would have is an exe file of the machine code which is produced interpreter no executable file is produced assembler and executable file is for compiler one high-level language statement can be translated into several machine codes interpreter one high-level language program can uh may require several machine code instructions to be executed one low level language statement is usually translated on uh into one machine code instruction and um yeah so on so forth then compiled programs are used without the compiler interpreter programs cannot be used without that representative assembled programs can be used without the assembly so you can see compile and assemble are quite similar because they all are dealing with um you know converting to machine code uh compile program is usually distributed for general use um interpreter is often used when a program is being developed and finally assembler is used for general use uh again you know this one is going to come into paper too that's one we're going to have a look at this right now so yeah that is that now we're going to have a break and i'm going to be setting up a previous video that i've done so i'm going to be playing that but again that's what we're going to do so just a 5 minute break and then i'm going to play the video hey guys welcome back to another video today we're going to be looking at security and ethics in the computer science syllabus so further do let's begin so in this video you'll be looking at how we can keep data safe um and if it's not safe what are the actions that we can do we'll also be looking at how we can keep the data like basically the preventions and also the causes of where of data or when keeping data safe we'll also be looking at the uses of passwords firewalls proxy servers ssl tls and encryption so those are basically all terms of how we can prevent uh identity theft or when delta being stolen we'll also be looking at some risks by fishing farming hacking you know the the common ways of how data is stolen and we'll also be looking at some security safeguards when carrying out online transactions and computer ethics before we start this video uh the current source where i'm reading all of these notes will be down in the description it is an igcc textbook and can be solely trusted so let's begin with the introduction keeping data safe is very important and we all know nowadays everything is gone online so keeping dollar safe is very important because nowadays retrieving data from somewhere is becoming so easily because people are not that careful so much data is stolen from your relatives or an individual that's using a computer and therefore we're learning this chapter to ensure that our data is safe at all costs now data can be corrupted or deleted either through accidental damage or to a malicious act we look at the malicious acts and how we can also prevent these malicious acts as we go on in video and there are many ways to keep the data safe and so in this video we will look at the different ways we can keep this safe and also look at the causes of these identity thefts like example if someone does this malicious act what will happen to your computer or what can they gain and what's the best solution to do at that appropriate time so let's begin with security and data integrity so whether user is working on an offline computer or a computer connected to the internet keeping data is very important so again keeping look at this it's saying even offline so some people uh think that you can only get data stolen if your computer is connected to the wi-fi but that's wrong because data can also be uh stolen when it's offline and we look at the ways how offline online and all sorts of stuff like that tara is threatened by the malicious software hackers or accidental damage and this section covers a number of different security risks and considers ways to overcome or minimize minimize them sorry about that okay so we're going to be looking at the different security risks and how we can overcome them we just simple precautions and it can help so much can reduce a lot of uh stress either if it's your bank account detail or personal information that's stolen so if you just do these small tasks you can you can basically prevent so much headache and stress and all of that but just doing simple tasks that can save a lot of data from your computer because nowadays everyone is using computers and hackers are just getting a better way to steal data and uh hackers are just becoming better and better and therefore we ourselves have to also be aware of everything and therefore we're learning this chapter to ensure we can reduce the security risk and be aware of what we're doing in the computer so let's begin we're going to be starting with hacking so we're going to be looking at the different security threats or aspects when someone steals data from your computer so we're going to start with hacking and we all know the word hacking comes in so many movies series and everyone talks about hacking but in the computer science term hacking is the gaining of illegal access to a computer system so in a computer science uh exam for example it tells you to mention or tells you to state what is hacking you simply have to say this is the act of gaining illegal access to a computer system and the keyword here is illegal access so when you're writing this in your exam they will be looking at gaining of illegal access and then the second mark would be to a computer system because hacking right now we're looking at it in terms of a computer and how data is stolen from a computer system and therefore hacking is basically the act of gaining illegal access to a computer system so hacking let's look at some of the causes let's look at some of the preventions that we can do in to reduce the impact of hacking so the first cause of hacking when someone performs hacking what happens so hacking will often lead to identity theft or gaining personal information now throughout this video i've been saying identity theft that simply means that i can get information about you maybe your address where you stay or maybe some family relative details uh you know all those information that is personal and not meant to be told to anyone else like bank details and so on so forth those are basically called personal information and identity theft is basically that okay when someone is getting to know you that is to be personal so someone should not know about it but with hacking they're able to get those informations the next one is that data can be deleted changed or corrupted on your computer we have data and we have done that in the input output devices uh storage devices since if you've been doing computer science ict you've been knowing that data is always stored we have data we have information data is basically stored in um in the computer and with hacking they give or they get an opportunity to steal that data from your computer they can steal it they can change it they can also delete they can wipe out the entire data of the computer and they can also corrupt the data and when you say corrupt the data that also simply means to change the data or when corrupting the data basically adding something to it which can cause it to corrupt so that's what we that's what happens when hacking occurs so when someone hacks you have the following impacts to your computer now let's look at a way on how we can prevent these they're hacking let's see how we can prevent hacking number one is firewalls and i think you've heard about firewalls it's a very common term in computer science but i think we'll look at firewalls later on this video will look at it more in depth on what is firewalls how firewalls uh help uh but for now you just need to know that we use firewalls for hacking uh suddenly is that we use strong passwords and user ids uh using strong passwords can be very important because number one that can make the hacker or make hacking more harder when you have a strong password because it's harder to get access to the computer system and therefore use strong passwords and user ids to make it much more harder for the hacker to gain access the next one is using the anti-hacking software anti-hacking software basically gives you an alert that maybe someone is trying to if you get access to a computer and you can then take action according to what that software tells you to do so basically anti-hacking software so any software in general will basically alert you or uh some of the softwares can also do the action uh and and give you like a notification saying that someone is trying to give you access we have done so forth so we've done this this this okay so that's what we say by software so we've looked at the preventions we've looked at the causes we've looked at what hacking is and uh now let's look at the difference between cracking and hacking okay so this can be an exam question too you can say what is the difference between hacking and cracking so we said that hacking is breaking into a computer system to steal personal data without the owner's consent okay but the owner doesn't know or the user doesn't know that they're getting hacked but for cracking it's when someone edits a program source code for a purpose okay and this can be a purpose as in uh to see what has happened or uh to see if the code is altered or to see if a software is legitimate um and that's where we use a cracker so cracker is aware so the user is aware of what they're doing because the cracker will see if their software is indeed corrupted changed or deleted but for hacking the user does not know so that's the difference between hacking and cracking let's move on to the next one we say viruses uh what is a virus now this is not the ongoing viruses like the kovid but the viruses in a computer system is simply a code that replicates in to the computer system with an intention of deleting corrupting or can cause the computer to malfunction so viruses indeed are just like the real life where you know they spread so does it in a computer system basically it replicates itself with an intention of deleting corrupting files just like the real life viruses let's have a look at the causes of the preventions we're looking at the causes we have can cause the computer to crash stop functioning normally or become unresponsive now usually how a computer can be slow is one of the side effects of viruses okay when your computer system is slowing down it's very slow as day progresses that means that there's a virus in it's not a must that it's a virus but you should look into it but sometimes if your computer is slow it can be because of um memory maybe it's full but one of the effects is that if your computer system is getting slower it is because of viruses the next one is it can delete files and data as we said in the definition it replicates itself in an intention to delete or change data or corrupting the files so these are just some prevention sorry these are some causes that are done by the virus let's have a look at the preventions now with the preventions we have user antivirus software and uh just like the other like hacking with the anti-hacking software it's the same thing the same way the anti-virus software works basically it gives you a notification that there's a virus to this necessary actions to prevent it the next one is don't use softwares from unknown sources now usually nowadays uh so many people are getting a lot of information from the internet because it's free for example movies which is the best example you can give now many people nowadays search for movies online and they uh go to websites and those websites actually install viruses into your computer which replicates itself to delete utter and you will not notice this until you you know it's very hard to notice the virus unless you have antivirus softwares or uh you can notice your computer being slow and therefore uh try to avoid visiting websites like that and usually only visit secure websites and later on we'll see on how to determine if a website is secure we look at uh ways to know that this website is secure and it is good to um enter it now usually if you use antivirus software underwater software basically also uh gives you a notification that this uh website is harmful and therefore don't use it okay so that can also be a plus point of using an attabar software and finally the next prevention is be careful when opening email so many people have spam emails but nowadays uh google emails are becoming more smarter they are categorizing each email like spam and all but be careful when opening emails attachments from unknown senders so if you're not you're not aware about them avoid opening them okay let's move on to the next security threat which is fishing so we have fishing farming and uh fishing and farming okay so let's look at fishing and let's look at farming so we're looking at fishing this is when the creator sends a legitimate looking email and as soon as the user clicks on the link it is redirected to a fake focus website and this fake focus website is therefore then stealing data or helps to gain a bank account details or so forth so for basically personal data so let's look at the causes the first one is that once when the user clicks on the email uh or the the email when it's redirected to the website this can allow the user whoever is behind this hacking or behind the fishing will basically be able to gain the personal data such as the bank account details uh you know family members numbers of users of the computer and so forth so on so forth okay the next cause is that this can lead to fraud or identity theft again uh most of these uh security threats are leading to identity theft if you've noticed so why would someone want identity theft why would someone want to know where you live now this could be a threat okay okay you can email or you can message them saying that i have your address send me this amount of money or else i will sort of do this this okay and therefore the user gets scared and gives them money this is what we call identity theft so let's look at the prevention z preventions is using isps filter out the phishing emails as i told you now uh internet is also becoming smarter and therefore we are categorizing different emails and this can basically reduce the fraud emails can reduce these phishing emails aside so you don't even open it so we use the isps filters to filter out all of these phishing emails the next prevention is that the user should always be cautious when opening emails or attachments just like the previous one with viruses it's the same thing always be cautious and most of these i uh most of these hacking theft or most of these hacking uh or what we say security threats you always have to be cautious you have to always be aware of what you're doing in the computer system and therefore most of these people target the old people because they're not as informative i would say or they're not that they're not with information they don't have enough information on how to use the computer and therefore sometimes they get lost and therefore it's a very easy target to get you know whatever they want uh either it can be personal lottery or money bank account details anything okay so therefore they target the appropriate uh age or appropriate population for an easy task but therefore uh i think everyone needs to be aware of what they're doing and let's move on actually and uh let's move on to farming so fishing and farming performing is a malicious code that is installed on a user's hard drive or on the web server and this code will be direct to a fake bogus website without their knowledge so you can see phishing and forming both redirects to a fake bogus website but the difference is that farming is a malicious code while phishing is basically when they send a legitimate email which then redirects to a fakebox website so let's look at the causes of the forming and the causes are the creator of the malicious code can gain prison water just like the others and this can lead to identity theft just like the others again the next one is that some of the anti-spyware software can be identified so again we use as power again for the preventions for this you use isps there's no uh software to reduce this this one you just be aware uh with this one we have antivirus we have anti hacking so we have quite some softwares nowadays to help us so this one we can use the anti-spyware okay and uh the user should always be alert and uh look for clues that they've been redirected to another website uh let's move on to war driving so war driving is simply the gaining or is basically when you locate and use wireless uh internet connections illegally without someone knowing so if i use your internet connection without you knowing that's basically called or driving the causes would be that you can steal a user's internet time and uh this basically means that if i steal your users into the time if i steal your internet time that will just reduce the internet speed and you if you've noticed that if many of your family members use the wi-fi the wi-fi will reduce now me using your wi-fi will be another member and therefore slowing down the speed of the wi-fi which can basically steal the user's internet time the next one is that it is possible to hack into the wireless network and steal the user's passwords and many other personal details so that's called what driving and that's the causes of port driving how we can prevent it is that we use a wide equivalent privacy their wep encryption okay we look at encryption again uh later on in the videos that you will come up that will come up and uh we also use firewalls that we that helps us to prevent the outsiders to gain access finally let's move on to spyware and then cookies and then in the next video we will be looking at the loss of data and data corruption okay so we will split this into two parts so that part one will only be looking at the different identity um theft or the different um security threats so let's look at spyware uh previously when we talked about farming we looked at anti-spyware so it should be something related to that but it is not so you think that the software means anti-spyware it does not mean like that okay so what we say a by spyware is basically when we gather information by monitoring key presses on the user's keyboard and then the information is sent back to the person who sent the software so this is basically we monitor what or or when someone monitors what you're typing to gain uh information and why would someone want to know what you're typing now for example if you visit a bank website okay and you input your password with your keyboard this will basically send it to the user who sent the spyware and can therefore get to know your bank account details and then can get money out of that so let's look at the causes of this against bioware is basically gathering information by monitoring key presses on the user's keyboard and then the information is sent back to the original originator we can say okay so when looking at the clauses gives the originator access to all data entered using a keyboard on the user's computer of course that's in the destination too and the software is able to install other spywares read cookie data and also change the user's default web browser so this is basically uh getting information from the computer how we can prevent this is number one using entice by software again gives you an alert that someone is trying to um basically monitor your key presses the next one is that the user should always be alert look for clues and thirdly is that when you're inputting any password in a website use your mouse uh try use your mouse because they cannot monitor the mouse finally let's move on to cookies a cookie is not a security thread but basically stores the data when you use a web browser okay so let's look at this definition a cookie is a packet of information that is sent by a web server to the web browser okay sent by the web server to the web browser and cookies are generated each time the user visits the website and normally nowadays if you go to a website people say that this website uses cookies accept and deny and stuff like that okay so usually most people just click on accept uh and without even knowing what they're doing so cookies are basically a packet of information that is collecting whenever using using a website so again it's saying a message is frequently displayed saying that cookies are required to access the website and basically you accept and every time a user visits the website the cookies will have collected the key information and store it in their web browser so what this means that when i uh go and log into one of the websites automatically maybe they log me and this is done because of the cookies they have just collected the key information about the user so whenever we go to the same website it will store the data so here's a good definition cookies aren't programs but are simply pieces of data it is not a security threat so whenever they ask you is cookie is a security threat and then exam question they are not security threat but simply programs that store data and they can't actually perform any operations but just allows uh detection of web pages viewed by the user and basically just stores and gathers information uh from the user when using the website and does not contain any personal information it's not stealing any personal information so there you go we looked at cookies looked at spyware we looked at wardriving farming phishing viruses hacking and we looked at some of the introduction to how some data can be stolen in the next video okay guys so that concludes the live stream thank you so much for watching this chapters on your screen is what we covered again if you want to practice on some extra questions down in the description i've put about three videos past paper questions where i go and have walk through of each of the past paper question on these chapters so we have done these eight chapters so hopefully you enjoyed this long long live stream i enjoyed it so hopefully you guys did um thank you for watching it and if you made it all the way i assure you you will do much better in the theory papers because this video is very thorough of every eight topics of every chapter it's very thorough so thank you for watching um