C++ Programming language Cheatsheet Cheatsheet




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

TypesData-type
Basicint, char, float, double, short, short int, long int etc
Derivedarray, pointer etc
User Defined Data Typestructure, 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

LiteralExample
Integer Literal- decimal255
Integer Literal- octal0377
Integer Literal- hexadecimal0xFF
Float point Literal53.0f, 79.02
Character literals'a', '1'
String literals"OneCompiler", "Foo"

Escape sequences

Escape sequenceDescription
\nNew line
\rCarriage Return
\?Question mark
\tHorizontal tab
\vVertical tab
\fForm feed
\Backslash
\'Single quotation
\"Double quotation
\0Null character
\bBack space

Operators

Operator typeDescription
Arithmetic Operator+ , - , * , / , %
comparision Operator< , > , <= , >=, != , ==
Bitwise Operator& , ^ ,
Logical Operator&& , ||, !
Assignment Operator= , += , -= , *= , /= , %=, <<=, >>=, &=, ^=, |=
Ternary Operator? :
sizeof operatorsizeof()

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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