Methods of calling functions 

Two types call by value and call by reference. 

1. Call by value: 

In call by value method the copy of the original value is passed to the function, if the function makes any change will not affect the original value.

Example

#include<iostream.h>

#include<conio.h> void

swap(int a, int b)

{ 

int temp; 

temp = a; 

a = b; 

b = temp; 

} 

main() 

{ 

clrscr(); 

int a,b; 

cout<<“Enter values for a and b:-“;

cin>>a>>b;

cout<<“The values before swap a =”<<a<<“and

b =”<<b;

swap(a,b);

cout<<“\nThe values before swap a =”<<a<<"and 

b =”<<b;

getch(); 

}

2. Call by reference:

In call by reference method the address of the original value is passed to the function, if the function makes any change will affect the original value. 

Example

#include<iostream.h>

#include<conio.h>

void swap(int &a, int &b) 

{ 

int temp; 

temp = a; 

a = b;

b = temp; 

} 

main() 

{ 

clrscrO; 

int a,b;

cout<<“Enter values for a and b:- “; 

cin>>a>>b;

cout<<“The values before swap a =”<<"

and

b="<<b;

swap(a,b);

cout<<“\nThe values before swap a =”<<a<<"and

b =”<<b;

getch(); 

}