Code with Mosh in CPP Part One

What is CPP

Recommended IDE: Clion

Cpp executable: Cpp 20

A project have a unique main file ended with .cpp postfix.

Case sensitive language - CPP

Type of value the function gonna return, followed by function name; After the function name, there is a pair parenthesis, followed by a pair of braces

Hash tag with angle bracket define the directive of our program;

Iostream - input output stream

std is short for standard library

This is like the bucket or container available for us

cout is short for character out, follow by two left angle bracket .

End each line of statement with semicolon.

Terminate it with a semicolon as it is a statement, A line is called a statement.

Run Code in IDE

CPP code needs to be compiled to machine code that can be run by the computer operating system.

Machine code is the native language that a computer’s operating system understands.

The bar (pane) under codes is called console window or terminal window.

Command + B to compile & build codes.

Command + R to run codes.

TOC

The content included in the ultimate c++ course from CodeWithMosh’s version. It is also shown in

Basic

• Fundametals of programming in C++
  * Variables and constants
  * Naming conventions
  * Mathematical expressions
  * Writing to and reading from the console
  * Working with the standard library
  * Comments
• Data types
• Loops
• Decision making statement
• Functions

Intermediate

• Arrays
• Pointers
• Strings
• Structures
• Enumrations
• Streams

Advanced

• Classes
• Exception
• Templates
• Containers

Foundamentals of CPP

Variables and constants

Variable - temporarily store data in computer’s memory

Also, it’s the name of location in memory where we can store some value.

Declare a variable in CPP

Data type + Meaningful Name + Assignment Operator (optional) + Value (optional);

Initializing variable is not mandatory, but good to follow;

Insights behind Swap A and B

Use another variable temp to hold the value of variable A, and give the value of variable B to A, give the value of temp to B.

Constants

Use constant to prevent some variable’s value from changing,

We type the “const” keyword before declaring this variable.

Naming convention

Snake Case, low case word with lower slash. hello_world_variable

Pascal Case, Capitalized the variable name. HelloWorldVariable

Camel Case, first lower case and rest word capitalised. helloWorldVariable

Mathematical Expressions

There is operator and operands in a expression, for example, in A+B, A and B is the operands

• Addition operator +
• Subtraction operator -
• Multiplication operator x
• Division operator /
• Modulus operator % returns the remainder of a devision

If both of operands are integers, it will not output a result of floating number tho,
At least, one of the operands is double type, so that the result could be floating number.

x++,++xand x=x+1

Only decrement and increment have notations like x++ and x--
They can be applied as a postfix or as a prefix, What is the difference between them then ?
E.g. ++x x++

int x = 10
int y = x++;

Postfix notation: first step the current value of x which is 10 will be assigned to variable y
And then X will be incremented by one
After this code block x will be 11, y will be 10

int x = 10
int z = ++x

Prefix notation: Use increment operator as a prefix, first step variable x will be incremented by one, and then the value of x will be stored in z.
So in that case both x and z will be 11

In mathematics, the multiplication and division always have a higher order or priority than addition or subtraction operators

We can always change order of these operators using parenthesis, wrap this in parenthesis

In the fraction ¾, four is the denominator.

Decimal part will gone if the declared variable to store it is integer.

Write to and Read from the Console

<< These double left angle brackets are called the stream insertion operator,

The operator for inserting something to our output stream.

std::endl == \n newline character to end a line.

cin along with the stream extraction operator,

It’s the opposite of stream insertion operator,

Stream extraction operator notation is double right angle brackets >>

Working with the standard library

With statement using namespace std; declared before main function,

We can simply access all objects in the STD namespace without double colons and std prefixed,

std::cin could be simplied to just cin in that way.

Comments

It’s more conventional to write a comment above a line

We can also start a mutiple-line comment with a forwar slash and an asterisk

Fundamental Data Type

C++ is statically type language

When declaring its type we need to specify its type and this type cannot be changed throughout the lifetime of our program

CPP‘s built in types

• Short
• Int
• Long
• Long long
• Float
• Double
• Long double
• Bool
• Char

If we don’t type f or l after float and long type variable’s value in assignment statement, compiler will treat them as double and int by default.

Key word auto leads our compiler to infer datatype.

Brace initialization, it could defaultly initialize a variable to zero and prevent it shows the random value in garabage before firsst assignment. Garbage makes program unpredictable. Also, it could prevent you from wrong type assignment,

Decimal part = fractional part

Warning on Numerical Variable Processing

• Decimal base 10
• Binary base 2
• Hexadecimal base 16

e.g. 0xFF = 0b11111111 = 255

Keyword “unsigned” numerical type should be stayed away, we don’t need every feature c plus plus has

Narrowing
Initializing a small type with a larger type
Compiler will narrow down our number
E.g.

int number =1000000;
short another = number;
cout << "another = " << another << endl

There is a warning before compilation, and after compilation, this is the result

16960

It’s the result of narrowing conversion

int number  = 1000000;
short another {number};

Brace initializer’s benefit in that case is compiler will prevent us from compiling it

“=” assignment operator

Generating a random number

Use the rand() function in ctdlib, everytime we run our code we get an exact same number. Because the so-called random is not that true random, it technically relys on some mathematical formula

Getting the current time to get a wilder seed

Time function calculate the elapsed seconds from 1th of Jan 1970

Variable and Argument

• Variable: A variable is a storage location in memory that can hold a value. Variables are used to store data that can change during the execution of a program. They have a name (identifier), a data type, and a value. Variables can be manipulated and used in expressions and statements.
• Arguments: Input values that are passed to a function or a method. When a function is called, the values passed to it are called arguments. These arguments are used by the function to perform specific tasks.

Argument and Parameter

• Parameters are the variables defined in a function’s declaration that specify what input the function expects.
• Arguments are the actual values or expressions that you provide when you call the function, which correspond to the parameters.

Hash Define Directive

must place the #define directive before the #include directive.

#define _USE_MATH_DEFINES
#include <cmath>

​ This way, the preprocessor will see the definition of _USE_MATH_DEFINES before it includes the header, and the mathematical constants will be available for use in your code. If place #define after it the preprocessor don’t get the instruction to do extra operation when replace #include because its sequence should be fixed

Circle area is equivalent to Pi times Radius to the power of 2