C++ Programming language Cheatsheet

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C++ is a widely used middle-level programming language which is used in developing major operating systems( Windows, Linux, Android, Ubuntu, iOS etc), Games, databases and compilers etc.

Basics

• cin >> x– read value into the variable x from input stream
• cout << x — printf value to the output stream
• // — single line comments
• /* */ — Multi line comments

Sample C program

#include <iostream>
using namespace std;
int main() {
    cout << "Hello World!!";
    return 0;
}  

• #include <iostream> — iostream is a inbuilt header library which allows you to deal with input and output objects like cout etc.
• using namespace std — Specifies that the object and variable names can be used from standard library.
• cout — to print the output.
• main() — main function is the entry point of any C++ program.
• return 0 — To end the main function

How to compile a program in C++

Open your terminal, Navigate to the directory where you have saved your program. Consider firstprogram.cpp is the name of your program.

sudo g++ -o firstprogram firstprogram.cpp

How to run a C++ program

./firstprogram

Data types

Types	Data-type
Basic	int, char, float, double, short, short int, long int etc
Derived	array, pointer etc
User Defined Data Type	structure, enum, Class, Union, Typedef

Variables

data-type variable-name = value;

int value = 10; // declaring int variable and assigning value 10 to it
char grade = 'A'; // declaring char variable and assigning value A to it

Naming convention

• only letters (both uppercase and lowercase letters), digits and underscore(_).
• cannot contain white spaces
• First letter should be either a letter or an underscore(_).
• Variable type can’t be changed
• Case sensitive

Arrays

data-type array-name[size]; // one-dimensional Array
data-type array-name[size][size]; // two-dimensional Array

Example:

int a[5] = {1,2,3,4,5};
int a[2][3] = {
                {1,2,3},
                {4,5,6}
              };

Literals or Constants

Literal	Example
Integer Literal- decimal	255
Integer Literal- octal	0377
Integer Literal- hexadecimal	0xFF
Float point Literal	53.0f, 79.02
Character literals	‘a’, ‘1’
String literals	“OneCompiler”, “Foo”

Escape sequences

Escape sequence	Description
\n	New line
\r	Carriage Return
?	Question mark
\t	Horizontal tab
\v	Vertical tab
\f	Form feed
\	Backslash
‘	Single quotation
“	Double quotation
\0	Null character
\b	Back space

Operators

Operator type	Description
Arithmetic Operator	+ , – , * , / , %
comparision Operator	< , > , <= , >=, != , ==
Bitwise Operator	& , ^ ,
Logical Operator	&& , `
Assignment Operator	= , += , -= , *= , /= , %=, <<=, >>=, &=, ^=, `
Ternary Operator	? :
sizeof operator	sizeof()

Conditional Statements

1. If

if(conditional-expression)
{
    //code
}

2. If-else

if(conditional-expression)
{
    //code
} else {
    //code
}

3. If-else-if ladder

if(conditional-expression-1)
{
    //code
} else if(conditional-expression-2) {
    //code
} else if(conditional-expression-3) {
    //code
}
....
else {
    //code
}

4. Switch

switch(conditional-expression){    
case value1:    
 //code    
 break;  //optional  
case value2:    
 //code    
 break;  //optional  
...    
    
default:     
 //code to be executed when all the above cases are not matched;    
} 

Loops

1. For

for(Initialization; Condition; Increment/decrement){  
//code  
} 

2. While

while(condition){  
//code 
}  

3. Do-While

do{  
//code 
} while(condition); 

Functions

Function is a sub-routine which contains set of statements.

// declaring a function
return_type function_name(parameters);

// defining a function
return_type function_name(parameters){  
//code
}

// calling a function
function_name (parameters)

Pointers

Pointer is a variable which holds the memory information(address) of another variable of same data type.

datatype *pointername;

Example

int x = 10, *ptr;

/*ptr = x; // Error because ptr is adress and x is value
*ptr = &x;  // Error because x is adress and ptr is value */

ptr = &x; // valid because &x and ptr are addresses
*ptr = x; // valid because both x and *ptr values 

Structures

Structure is a user-defined data type where it allows you to combine data of different data types.

struct structure_name {

   member definition;
   member definition;
   ...
   member definition;
} [one or more structure variables]; 

struct structure_name variable name; //declaring structure variables

Enum

Enumeration data type is a user-defined data type in C++. enum keyword is used to declare a new enumeration types in C++.

enum name{constant1, constant2, constant3, ....... } var-list;

Example

enum month{January, February, March,
                          April, May, June, July, 
                         August, September, October,
                         November, December} name;

Typedef

Typedef is used to explicitly define new data type names by using the keyword typedef. It defines a name for an existing data type but doesn’t create a new data type.

typedef data-type name;

Example

typedef unsigned int distance;  // typedef of int 

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