WEBVTT

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Hello, this is Juhwan Kim

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This is the second lecture of Unreal C++ basics

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In this lecture, we will learn C++ grammar

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We will get to know of C++'s data type, variables, and functions' meanings

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and I will explain them

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I will let you know how to interpret and use

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conditionals, iterations, and expressions

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Meaning of function in C++

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First, data type and variables

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Data type

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is the form for storing data

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Data is not refined

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The difference between data and information is

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whether it has a meaning or not

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Data type differs in size or expression method

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according to the type needed to put data in computer memory

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For example, there are types that can store integers

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floating points

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like decimals or fractions

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characters or strings

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boolean, enumerated, and void types

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Let me tell you about variables that can store various types like these

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As you can see in the table, there are various data types

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but the basic one is 'int'

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which stands for integer

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The content can vary

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but usually int has the size of 4 bytes

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It can express from -2.1 billion to 2.1 billion

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Unsigned int means int without a sign

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Since it does not have a sign, we ignore the negative numbers

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and it can express up to 4.2 billion

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Like this, there are short, unsigend short, long, unsinged long, float

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double, character, unsigned character data types

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Unlike int type that can only express integers

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float and double, which are real number types, are engineering expressions

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and it can express from 3.4*10^-38

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to 3.4*10^38

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When we talk about data type and variables

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you can consider variables as the bowl

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to put values expressed as the forementioned data types

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To put it easier, when you put a value into a bowl

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whether that be an integer, real number

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or a string

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it can become the integer 3

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real number 3.0

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or the string of 3

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the way that is desired

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So it is declared and defined based on the data type

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Now I'll tell you about declaration and definition of variables

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It is about grammars

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first the data type comes

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and then the variable name

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then an equal sign, and finally the value

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You also have to put a semicolon at the end

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For example, when you say int a = 3

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It means that in the variable named a with the data type of int

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the integer 3 is contained

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The next one says float fValue = 1.0f

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and this means

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it is in the form of a floating point

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In the variable named fValue

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with the data type of float, floating point

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the constant value 1.0f is contained

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The reason why there's an f at the end

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is to show that it's in a float type

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that is, a floating point type

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The next one says char c

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This means that the variable c in the form of a string

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is declared but not yet defined

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There is no value substituted so it is not defined

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and it is just declared that the variable character c will be used

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I explained briefly about data type and variables

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and next I'll talk about functions

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Functions are

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fundamentally the same with functions in maths

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In mathematics, they must be one-to-one

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and if there's an input there must be an output

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but in functions in programming, there does not need to be outputs

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So I'll tell you about return value which is the output, reference, and the mechanism

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To put it simply, function in programming is function in mathematics

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expanded in various forms

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In another way

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it is a defined element that can perform a function independently

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and a group of functions are called module

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And this function unit is at the core of structured programming

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Depending on programming languages, function names differ

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but function is the most basic form

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and sometimes it is called sub-routine

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Sub-routine means the same thing as function

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but it stresses that it diverges from the normal routine

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and comes back after performing

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It is also called method

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Method is used in languages like Java or C# that emphasize object orientation very much

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From the word function

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and expanding on the meaning of performing a function

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they use the word method meaning that it is about the methodology of it

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It is also called procedure

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Procedure is used to emphasize the server or the process

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saying that it performs something orderly

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Now we'll talk about the shape of the definition of functions

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There is int which is similar to variables

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and that is the type int

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which is a return type that I'll explain later

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int, space

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Add indicates the name of the function

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It is the name, and then parenthesis

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int A and int B

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These are the parameters of the function

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It is also called parameter(in Korean)

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which is the input of the function

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int on the left

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is the output data type

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and int a and int b on the right

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are parameters, which are the inputs

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Under that, there are curly brackets

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which indicate the body of the function

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The two slashes and the part that says function implementation

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is called the annotation which in programming

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is complied and does not have a meaning but that explains

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Then it says return a plus b

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To give you a brief explanation about this int a Add function

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it is a function receiving integers A and B

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and returning a plus b, the sum

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Let me give you an example of function definition order

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On the left, it says int main

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and void function 1, void function 2, void function 3

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3 functions are there

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It is a diagram showing the name of the function and its body

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Starting from int main

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it defines functions 1, 2, and 3

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Function definition

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puts a value into the parameter of a function and gets a return value after performing

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The int main in the example

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usually means the main function

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that performs in a console project

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and the main function is called the entry point

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When you run a program

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it will perform one by one starting from

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under the curly bracket under int main

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So it meets function 1

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meeting function 1 parenthesis

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it defines the first function, function 1

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Then the implementation flows

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to the void function 1

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on the top middle source

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Performs the function

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and when it meets return

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it comes back to function 1 on the left

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The process goes on

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and upon meeting function 2

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it goes to the bottom middle

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where void function 2 body is

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and again performs

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void function 2

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and the next step

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is where it meets the void function 3 definition

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Then void function 2

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defines function 3

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moving to void function 3

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on the right

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performing the function

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and coming back

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to void function 2 upon meeting the return

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Then again it meets return

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going back to the main function

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and performing what comes after the void function 3 parentheses

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The process can be shown with arrows

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Let me give you a bit more explanation

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on parameter that I mentioned before

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It is about

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ind Add function that I showed you

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Parameter is the part that indicates

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input in functions of mathematics

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When you have a function that adds two integers

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since you have to put two integers in

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you need to know how

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the two integers will be portrayed

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What's red here, that is

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int a and int b are the parameters

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If parameters are there like that

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from the part that uses the function

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we can put values in

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which are called arguments

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So, where it says int a and int b

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3 and 6 are put in

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3 is int a

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and 6 is int b

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So upon return

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We saw that it would return a plus b

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So on return

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we have the variable c

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c becomes return type

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or return value

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When I was first explaining the function

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int Add

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The int type at the very front of the function's name

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is the return type of the function

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The calculation will be done

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and it is returned in that int type

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In this case, it is 3 plus 6

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so 9 will be returned

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Return type and parameter type are together

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called function signature

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These are what have the function's

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form as signatures

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We didn't learn it yet

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but when you learn Lambda function or Delegate

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you will get to know about function signature

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To give a brief explanation, function signature is

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a grammar that expressed what function it is

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What you should note is that

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parameter, argument, signature and such

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are translated to

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formal parameter, actual parameter

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formal argument, actual argument, function signature

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and such

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and it would be great to organize these according to their meanings

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and learn them

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The reason why we use functions

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is to avoid having overlapping codes

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We can gather several duplicate codes

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and turn them into one

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That way, reading the code becomes easier

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and when you need to change the code

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only the body of the function needs to be edited

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and the part that defines doesn't need to be

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Functions are already used in console main

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and Unreal has countless functions

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They are used in application programming interface

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To put it easily

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in Unreal, to perform or run

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a function

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there is a function for that

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and there are many of them

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I gave a brief explanation about functions

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but apart from this

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there are many other topics on functions

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Call by value and call by reference

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determine whether a value

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or a pointer or reference will be input

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There is also recursion

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which is a function that defines itself

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You will also learn class' member function later on

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There is also function pointer

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which takes the defining part as the value

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so that the defining happens later

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meaning that the caller and callee are switched

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Statement and expression

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Next is statements

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Statements

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contain

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conditional statement, iteration statement, and break statement

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Statements, put easily

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are what controls the flow of a program

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The most basic example

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is an if statement

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if statements, according to certain conditions

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the divergence differ

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MSDN, Microsoft Development Network's

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website's URL on the bottom

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will give you an explanation on statements

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I will give you a brief explanation

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about how the code if works

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with a diagram

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On the left you can see a black circle

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which is one line of a code

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and at that point it meets a condition

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if a is true

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The triangle is called the diagram of the flowchart

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Depending on whether a is true or false

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the flow is divided

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If it's true, to the left

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and if false, to the right

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That was an example of an if statement

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and looking at the third diagram

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it uses continuous ifs

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where if then is used when the content of if is true

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and else is for when it's not

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When one condition is true

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it reaches end

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and if not

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it goes back to if

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00:14:19.400 --> 00:14:21.500
which is shown in this diagram

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There are many other conditionals

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00:14:23.200 --> 00:14:25.000
other than if conditional statements

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Switch-case has one condition

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and diverges multiple ways according to the value

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For example, depending on variable 2's value which can be 1, 2, or 3

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00:14:34.750 --> 00:14:37.650
it diverges to the right like this

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Iteration means repeating a certain statement

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and for statements

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is a statement that gives a variable a beginning

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and end point and which repeats according to conditions

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According to the condition in the middle

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it can also break

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While statement is also an iteration

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In case the condition inside while is true

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it repeats endlessly

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Do-while is a while with a condition

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that first performs

301
00:15:06.900 --> 00:15:10.150
and then keeps editing according to the conditions that follow

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Among interations

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it can break from the loop

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or keep performing

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00:15:18.000 --> 00:15:20.000
This is called break statements

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00:15:20.000 --> 00:15:22.900
Having break or continue

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00:15:22.900 --> 00:15:25.550
in the conditions

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00:15:25.550 --> 00:15:27.950
it can break from the cyclical loop

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or ignore it and continue

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Now let's move on to expressions

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Expressions

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00:15:38.250 --> 00:15:41.650
are elements like

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conditionals, values, variables, operator and function definition's

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combinations

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00:15:49.500 --> 00:15:52.900
Put simply, it is an equation that can be evaluated as value

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00:15:52.900 --> 00:15:56.800
Parts of the if statement like a is true or false

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or equal to 3 are expressions

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00:16:00.800 --> 00:16:04.050
There are formula and discriminant in expressions

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What must be mentioned along with expression is operator

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which is

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literally what operates

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Arithmetic it mathematics can be a good example

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There are many types of operators

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00:16:16.700 --> 00:16:21.050
which can also be seen on MSDN

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I made a table of operators

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There are operators with signs

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showing negative or positive

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and arithmetic operator

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00:16:32.500 --> 00:16:35.200
for arithmetics

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00:16:36.000 --> 00:16:40.900
and relational operators like not equal to, bigger or equal to, bigger, and smaller

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logical operators

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00:16:44.600 --> 00:16:47.000
and operator and or operator

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00:16:47.000 --> 00:16:51.000
cast operator that changes types

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00:16:51.000 --> 00:16:56.500
increment and decrement operators, assignment operator, comma operator, and sizeof operator

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There are various operators in C++

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Let me explain the most basic operator

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On the screen it says a=1

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In mathematics, this means that you substitute a with 1

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and in C++ as well, the constant 1 is substituted with the variable a

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The two equations under that

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are statements that increase the value of the variable a

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but the expression is a bit different

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The one on the left is substituting variable a with the value of a+1

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If the value of the variable a was 3

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3+1 is 4 so 4 is put in

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making a increase by 1

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The one on the right is a simplified version of the one on the left

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which means

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substituting a that is increased by 1

350
00:17:47.800 --> 00:17:52.000
Increment and decrement operator can also be used to express a increasing by 1

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00:17:52.000 --> 00:17:56.200
It can be simplified even more to a++ or ++a

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Prefix and postfix expressions' difference is the order of

353
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substitution and reflection

354
00:18:04.000 --> 00:18:06.300
Relational operator is similar to mathematics

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00:18:06.300 --> 00:18:09.000
and depends on the value of true or false

356
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Equality operators are similar to math as well

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and truth or falsity depends on whether it is equal or not

358
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Conditional operators diverge according to certain conditions

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00:18:20.150 --> 00:18:23.000
which is similar to if statements

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00:18:23.000 --> 00:18:26.000
According to the truth value of the

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00:18:26.000 --> 00:18:27.650
statement inside the parentheses

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00:18:27.650 --> 00:18:30.850
D or E next to the question mark is performed

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00:18:30.850 --> 00:18:32.200
Next is cast operator

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Cast operator changes types

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It can change an int value

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to a float value that can have a real number

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It's not as simple as just changing types

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because integer 3.3 and real number 3.0 are different values

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So there needs to be a process of changing the value

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and a specific explanation can be found on the MSN page

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There are orders in operators

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You would have learned in mathematics

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but when there are several operators

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orders determine what is performed first

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Operators have orders and combination directions and rules

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For example, in mathematics, multiplication

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comes before addition

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and it is similar in operators

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When you're unsure of the order

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00:19:24.750 --> 00:19:27.700
you can use parentheses that force orders

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Now we'll move on to C++ operators' orders and associativity

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On the top, there are square brackets, parentheses, period, arrow, ++ and --

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00:19:40.650 --> 00:19:44.600
which are increment and decrement operators that use equations

384
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When these operators are put in equations

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the calculation is done from left to right

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Simply, ++ operator

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00:19:54.400 --> 00:20:02.000
in a++ means that a increases

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Second, sizeof, ampersand, asterisk

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which are and and multiplication

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00:20:11.250 --> 00:20:18.700
+, -, ~, !, and ++ and -- for prefix

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These are unary operator with one operand

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00:20:22.000 --> 00:20:26.700
These are operators that work on one subject

393
00:20:26.700 --> 00:20:32.000
and sizeof can figure out the size of a variable

394
00:20:32.000 --> 00:20:37.000
so it looks like sizeof(variable)

395
00:20:37.000 --> 00:20:41.000
& and * are put before a variable

396
00:20:41.000 --> 00:20:47.850
to bring value from the address value of that variable

397
00:20:47.850 --> 00:20:51.000
+ and - operator that are not addition and subtraction

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00:20:51.000 --> 00:20:54.800
represent positive or negative numbers

399
00:20:54.800 --> 00:20:58.000
and it lets us know the sign of a variable

400
00:20:58.000 --> 00:21:00.450
These are unary operators

401
00:21:00.600 --> 00:21:04.400
and in this case, the operator works when it is put from right to left

402
00:21:04.400 --> 00:21:07.200
You could think of -a or +a

403
00:21:07.200 --> 00:21:10.000
Casting operator is also unary

404
00:21:10.000 --> 00:21:13.400
and it casts one variable or type

405
00:21:13.400 --> 00:21:16.000
and changes it

406
00:21:16.000 --> 00:21:19.650
Next we have multiplication, division, and remainder operator

407
00:21:19.650 --> 00:21:22.350
which are related to multiplication

408
00:21:22.350 --> 00:21:24.000
and have two operands

409
00:21:24.000 --> 00:21:27.350
like multiplying A and B or dividing C by D

410
00:21:27.350 --> 00:21:31.450
They are operators that calculate the remainder of two values

411
00:21:31.450 --> 00:21:34.650
It goes from left to right

412
00:21:34.650 --> 00:21:37.350
like multiplying 3 by 2

413
00:21:37.350 --> 00:21:40.100
There are also shift operator and relation operator

414
00:21:40.100 --> 00:21:43.800
Shift operator shifts bit

415
00:21:43.800 --> 00:21:47.450
which moves binary numbers

416
00:21:47.450 --> 00:21:51.550
and also makes the result of multiplication by 2

417
00:21:51.550 --> 00:21:56.550
Relation operator includes larger than or smaller than

418
00:21:56.550 --> 00:21:59.150
like A is smaller than B

419
00:21:59.150 --> 00:22:02.650
or A is larger than B

420
00:22:02.650 --> 00:22:06.250
On the second page, there is equality operator

421
00:22:06.250 --> 00:22:09.400
In mathematics, only one = is used

422
00:22:09.400 --> 00:22:11.300
but in programming, two are used

423
00:22:11.300 --> 00:22:15.000
== means A is equal to B

424
00:22:15.000 --> 00:22:19.300
and != means A is not equal to B

425
00:22:19.300 --> 00:22:22.900
This also goes from left to right

426
00:22:22.900 --> 00:22:25.000
so it is read as A is equal to B

427
00:22:25.000 --> 00:22:28.450
A==B means

428
00:22:28.450 --> 00:22:32.200
A equals to B, not B is equal to A

429
00:22:32.200 --> 00:22:37.000
Bit operators are operators for bits

430
00:22:37.000 --> 00:22:44.750
logically like AND and OR

431
00:22:44.750 --> 00:22:46.650
and this also has the same

432
00:22:46.650 --> 00:22:50.250
order as equality operator

433
00:22:50.250 --> 00:22:55.450
There are also conditionals, simple and compound assignment, and sequential operators

434
00:22:55.450 --> 00:22:59.850
which also, like the ones mentioned earlier

435
00:22:59.850 --> 00:23:03.000
paying attention to the order must be noted

436
00:23:03.751 --> 00:23:05.201
Meaning of functions in C++
Data type
The form to store data in computer memory

437
00:23:05.201 --> 00:23:06.801
int(integer), float(floating point), char(character), std::string(string), bool(boolean), void

438
00:23:06.801 --> 00:23:07.952
Variable
The bowl for values, declared and defined based on data type

439
00:23:07.952 --> 00:23:10.853
Function
Element that can independently perform a function
Avoids duplicate codes
Only edits function body when changing code

440
00:23:10.853 --> 00:23:12.717
Statements and expressions
Statements
What controls the flow of a program

441
00:23:12.718 --> 00:23:14.268
Conditionals: if, switch-case
Iterations: for, while, do-while
Break: break, continue

442
00:23:14.268 --> 00:23:16.400
Expressions
Combination of elements like value, variable, operator and function definition
Operator: sign operator, arithmetic operator, relational operator, logical operator, cast operator, increment and decrement operator

443
00:23:16.400 --> 00:23:18.250
substitution operator, conditional operator, comma operator, sizeof operator
Must pay attention to the orders and associativity

444
00:23:18.250 --> 00:23:19.250
The End