C++ Variables

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Variables are data name that may be used to store a value. Variable may take different values at different times during execution.


Variables are may refer to some data types which are like int, float, char and etc.


Every variable in C++ language has a specific type that determines the layout and size of the variable’s memory. The ranges of the values that can store with the memory and set of operations that can apply to the variable.

C++ Variables

Syntax of variables

type variable_list;

Example of some valid variable declaration

int    a,b;
char   c;
float  d,month;
double k,salary;

Rules for variable declaration

  • A variable will have alphabets, digits, and underscore. Example: int _ab,a1,ab;
  • No white area is allowed at intervals variable name. Example: int a b;
  • A variable name will begin with alphabet and underscore solely. Example: int _ab;
  • A variable name should not begin with the digit. Example: int 5;
  • A variable name should not be any reserved word or keyword. Example: float, int and etc.
notepad

Lower and uppercase letters are distinct because C++ is case-sensitive.

Types of variables

  • Local variable
  • Global variable
  • Static variable
  • Automatic variable
  • External variable

Local variable

Local variables are used in within the function only, these variables won’t work outside of the function.

void function(){
	int a=10;	// Local variable
}

Global variable

Global variables are used in the entire program, these will work anywhere in the program. These variables are defined outside of the function.

int b=20;	// Global variable
void function(){
	int a=10;	// Local variable
}

External Variable

External Variable declared with extern keyword. when you declare extern keyword for the variable then it can access in one or more source file.

file.h
extern int x=10;	//external variable (also global)  
-------------------------------------------------------
#include  
#include "file.h"  
void printValue(){  
		cout << "Global variable";  
        cout << x;
}

Static Variable

Static Variable is declared with static keyword.

void function1(){  
	int a=10;	//local variable  
	static int b=10;	//static variable   
	cout << a << b;
	b++; 
}
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