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good morning everyone and welcome back
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to the study shoe project my name is
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mani and for those of you that don't
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know me I am a fourth year studying
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computer science and philosophy at the
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University of Oxford and today I'm going
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to bring you a video on the basics of
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coding I know that a lot of you are
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probably thinking that coding is this
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like crazy evil genius thing that just
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requires you to be the most intensely
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smart and academic person out there and
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requires so much understanding of hoodie
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things but that's just not true let's
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just take all our preconceived ideas
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about coding and put them on the side
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just pop them down and today I'm gonna
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spend a couple of minutes just telling
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you the basics of some of the key ideas
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that are involved in coding and by the
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end of this video hopefully together we
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would have written our first program 3 2
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1 let's get into this so I'm gonna be
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doing this sort of split screen style
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thing cuz I'm trying to be such as a
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professional youtuber why would you want
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to start why do you want to learn how to
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code coding is an invaluable skill and
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as we move into the future of the world
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whatever the future holds
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coding is going to be a net almost a
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necessary skill and I remind computer
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science teacher in school telling me be
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programming or coding whatever language
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you want to learn is the English of the
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future and it's one of those kind of
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skills that you can learn to do it at
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home not have a degree in it and get a
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job as a software engineer or a back-end
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stack engineer or whatever and without
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having the formal qualification because
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it is just one of those skills that they
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don't require you to have a formal
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qualification if you're good if you can
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show them that you are skillful within
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this domain then you'll get a job and
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some of these jobs are ridiculously
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high-paying so if by the end this video
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if you do a drawing doing I'm gonna put
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some links in the description box below
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so you can check out some more resources
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yourself it's what we're gonna cover
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today is some initial ideas of what some
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statements are how statements come
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together to put a program together and
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then we're gonna build our first basic
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program so first we gonna look at what a
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statement is now a statement can be any
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sort of single line of code doesn't
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necessarily even have to be on a single
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line
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that's just one way to sort of explain
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it to you now the first kind of
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statement we're going to look at is a
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variable assignment so what we're doing
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is let's say I type x equals 1 now it's
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important to understand that in
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programming the e is not thought of the
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same way as we look at equals in
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mathematics so in maths equals can mean
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a 1 equals 2 that doesn't make sense to
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us if you write a equals 1 that means
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they're both exactly the same thing
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however in computer science we have to
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remember the equals is assigning
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something when we have a equals 1 a is
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an empty box that we've just got above
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throwing one inside of it we're
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assigning something to it equally we
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could say a x equals hello
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that means we're putting the word hello
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inside this box X now the cool thing is
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that when we create a variable like X
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this variable can have any type so this
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could be an integer a string which means
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a series of letters put together so word
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sensors etc it could be just a single
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character there are many different
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things and these are known as tough as
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data types so let's say I just want to
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have I want to have variable X and we're
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going to make sure that it's an integer
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so here I've declared that it's int X
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and I'm going to give it the value to
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now put the semicolon show that this
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line is over now this kind of syntax
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varies across programming languages but
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here I'm just assuming that when using a
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sort of Java like language so we've got
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int x equals 2 now hopefully we've all
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understood that we've created a variable
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X and the data type of that variable is
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int so that means we've specified that
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this variable is going to be assigned a
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number at some point may not be but
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that's the type of data that we're going
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to put inside the box that we've labeled
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X so that's one kind of statement now
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what we can do is we can control the
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flow of data using other kinds of
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statements one of them is known as an
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if-then statement so if I write if and
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what this does is allows me to perform
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an action based on a certain condition
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so I write if x equals 2 then and then I
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can put inside these brackets what I
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want to happen print yes
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so that means when I run this program
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it's gonna check the value of X and
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that's done with two equal sorry he's
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gonna check the value of X and then if
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this is true it's gonna perform what's
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in the brackets and if it isn't it's
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gonna do nothing if we want we can add
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an else clause which means that if that
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isn't if if whatever's in those brackets
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doesn't hold you can perform a different
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action we can say print no so an if-then
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statement is just one kind of way that
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we can kind of control the flow of what
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is happening based on variables that
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we've created or different things that
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are happening in the program now you
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might be thinking ghost is great but how
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does this help me make an application or
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do things like that and these kind of
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small things can be built up to create
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more complex programs later on we're
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going to be looking at how we can create
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a program that will check whether a
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number is divisible by another number
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and it's really important to have these
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kind of if clauses to help us with them
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another type of way to control the flow
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of data is a while Clause now some of my
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guests it a wild statement works by
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rather than checking if what Evers in
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the bracket works is going to keep
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looping while whatever is in the bracket
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is still true so if I say while X is
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greater than what X is less than 0
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[Music]
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keep performing what's in here x equals
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X minus 1 now the first thing you're all
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probably thinking is that makes no sense
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whatsoever X doesn't equal X minus 1 it
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can never equal X minus 1 and again we
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have to remember here that equals is not
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the same kind of equals as it is in
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maths equals here is a variable
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assignment so here what we're doing is
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we're we're saying that whatever X held
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it's now going to hold 1 less than that
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we're going to look inside a box see
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what value X had take 1 away from it and
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then assign that to X and we're gonna
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keep doing that until X is less than 0
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we've learned how to make statements
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that have variables in them we've
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learned how we can flow the control of
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data using if statement and while loops
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now we're going to see if we can put
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those together to create the basic
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program checking whether one number is
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divisible by another what I'm going to
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do is we're first going to do this
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without using any sort of specific
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programming language and then we're
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going to put this in a compiler big word
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scary I know but we're gonna get through
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it and we're going to see whether and
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we're gonna write it in Java and then
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see whether our program works and if we
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have any issues when we think about
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creating a funner program to do
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something in this case we're going to
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give it two numbers we're gonna have to
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have an input we're going to make use of
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a function now functions just like in
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math we're going to map some inputs to
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some outputs now in this case the
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problem that we're solving is we're
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giving two numbers or checking if
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they're divisible so we're going to take
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two inputs so let's say we're going to
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create a function and we're going to
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call it divisible this is simple in X
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and in Y so a specifying that we're
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gonna give it two integers look at the
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body of this method and see what exactly
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are we putting inside this method what
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we do want this function to do because
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if we just said return
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X now this is just a function that is
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taking two numbers of returning the
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first one if we said return why it's
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taking two numbers and returning the
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second one so we can see how we can
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actually build up programs like this so
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what we want to do is we want to check
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whether the first number can be
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divisible by the second so the way that
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we're going to do this is we're going to
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use a while loop and the logic behind it
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is we're going to take the first number
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and we're going to keep subtracting the
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second number as many times as we can
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until that number so if we have 25 and
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we have five we're going to keep
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subtracting five from 25 until that
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number is less than the number that
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we're dividing by if that makes sense if
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you haven't understood that take a
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second to think about it we're going to
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take our big number we're going to take
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the number that we want to check whether
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it's divisible by this other number
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we're going to keep taking it away on
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until it is until it's smaller than this
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number then what we can do is you can
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check if that leftover number is zero
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that means we've been able to divide it
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perfectly each that we've been able to
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subtract that number perfectly each time
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but if it's in between zero and that
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number that means it's clearly not a
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divisor now the way that we can
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implement that note that logic into this
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code is by checking so while X is
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greater and then within the body of this
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code we can say x equals X minus y now
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do we remember why that equals is
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totally okay and doesn't feel well
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because it's assigning a new value what
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X is greater than equal to Y we're going
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to say x equals X minus y and that means
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when this loop terminates and that means
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this is no longer satisfied and so that
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means X is a less than Y so now how how
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is it we can check whether this is
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divisible once that loop is over we're
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going to say use our if statements that
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we learned about if x equals zero for
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checking so he's a double equals
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then print yes else no okay so if you
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haven't understood that rewind and see
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whether you understand the logic behind
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that again don't focus on the syntax of
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what we're writing just focus on whether
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you understand the logic of this program
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so we're inserting two numbers I wrote
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one out but yes or no depending on
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whether the first number is divisible by
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the second number we're going to keep
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subtracting the second number from the
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first number until that number is no
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longer bigger than the first one that's
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the underlying assumption that we've
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made and then once that number has
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become so small that it we can no longer
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subtract that without it becoming
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negative we'll check if that number is
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zero or not now we're gonna do is go
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onto an online Java compiler put all of
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this in Java and see whether it works so
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now what I'm doing is converting this
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sort of pseudocode that we've created
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which means code and programs aren't in
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a specific language but are basically
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showing us the logic so we easily
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created that using just the logic and
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now I'm gonna convert that into Java so
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each language has its own syntax so in
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some languages you put semicolons after
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every line and something you don't in
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some you write if-then and some you just
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write if in brackets so there's a lot of
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confusion amongst different languages I
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would recommend you just sort of kick
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one Java Python there generally a
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simpler ones to begin with and sort of
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take a go so I'm what I'm going to do is
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compile this in Java so it's just an
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online Java compiler so when you run a
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program your main classes what sort of
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runs anything that happens at the main
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class going to be called so what I'm
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going to do is call a function in the
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main class and then create that function
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that we just made below so we can refer
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to it so to think about it as this the
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main class is a to-do list of what's
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going to happen the moment you execute a
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program if you create a function that
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isn't in the main class sort of down
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here
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but you haven't referred to in the main
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class it's not going to run because it
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wasn't on today's to-do list so if I
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create a function call it huh so just
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ignore all of this stuff for now
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so we're going to call the function
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divisible and we're going to say that it
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takes two arguments so two inputs
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arguments as a formal word for that and
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we're going to say we're going to start
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now looking at what looking at our
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program so while X is greater than equal
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to Y x equals X minus y so this is going
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to end when that the condition no longer
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hold so now we're going to check if X is
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equal to zero then system
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[Music]
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dot out dot print line just e again this
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is just Java syntax on how you print
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something print and then we can add an
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else say it's cool select run so now
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again we've created this function but we
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haven't called in the main class notes
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and not nothing is going to happen so if
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I go here and I say divisible I'm
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calling the function divisible let's say
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25 and 5 and divisible to make sure it's
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not just giving us correct for
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everything select execute and see what
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happened so now we could do a bunch of
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errors so clearly I have screwed up
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somewhere it's always easy to see which
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where these errors come from because
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it'll show you there's a little arrow
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pointing here there's an error here so
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if ok this is me screwing up because
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Java doesn't use thenns so Java you just
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say if and you check let's try that okay
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so I'm forgetting some semicolon so
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there should be a semicolon there and
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I'm forgetting see where no one is
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perfect at all should be a semicolon in
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there let's try that
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okay what's wrong a hair stop divisible
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incorrectly
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so bit of an idiot there see perfect so
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yes it is divisible and no it is not
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divisible and there we go we've just
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written a program on checking well the
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two numbers are divisible and you didn't
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even know how to program beginning of
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this and if you did sorry it's not been
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quite easy for you so I'm really sorry
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that we do this but yeah so that was
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such a simple way of putting a program
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together I know that they've got the
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sort of the syntax of Java may not be
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that straightforward but I will put some
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online courses underneath to kind of
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give you and to see if that can help
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yeah I'm very proud of us together we
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have learnt again recapping we've learnt
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how to create variables how to use if
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statements how to use loops put them
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together to create a function test that
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function now debug it with some errors
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you are basically a full page computer
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scientists if you enjoyed this there's
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probably a good chance that you will
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enjoy programming in general so do check
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out it's a valuable skill to pick up and
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if you have some time this summer try it
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out you never know you might be the next
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Mark Zuckerberg you might rogram us out
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of this mess of coronavirus yeah either
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way I hope you enjoyed this video I
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really tried to break it down as much as
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I could I'm hope I hope you guys are
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having a great day wherever you are and
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that you found this video somewhat
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useful if you haven't checked out my own
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personal channel it is this is Manny and
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I've linked it down below and yeah
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thanks for watching guys and I will see
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you guys soon bye don't forget to
00:15:31
subscribe if you haven't
