C Program to Swap Two Numbers / Variables using Pointer

#include<stdio.h>

void swap( int *num1, int *num2)
{
    int temp ;
    temp  = *num1 ;
    *num1 = *num2 ;
    *num2 = temp ;
}

int main( )
{
    int num1,num2;

    printf("\nEnter the first number : ");
    scanf("%d",&num1);
    printf("\nEnter the Second number : ");
    scanf("%d",&num2);
    swap(&num1,&num2) ;
    printf("\nFirst number  : %d",num1);
    printf("\nSecond number : %d",num2);

    return(0);
}

Output :

Enter the first number  : 12
Enter the Second number : 22
First number  : 22
Second number : 12

Explanation : Swapping Two Variables using Pointer

Firstly we need to accept two numbers using scanf statement like this -

printf("\nEnter the first number : ");
scanf("%d",&num1);

printf("\nEnter the Second number : ");
scanf("%d",&num2);

Now You need to pass the address of both variables to the function. Parameter passing scheme is called as Pass by Pointer.

swap(&num1,&num2) ;

Now Take a look at function definition, We have passed address of two variables from main function to swap function. So we need variable container that can store the address of integer variables i.e Integer Pointers.

void swap( int *num1, int *num2)

Thus address of first number will be collected in “num1” pointer variable and second number will be collected in “num2” pointer variable.

{
    int temp ;
    temp  = *num1 ;
    *num1 = *num2 ;
    *num2 = temp ;
}