Program to interchange the value of two variable from call by value

/* program to interchange the value of two variable from call by value */
#include<stdio.h>
main ( )
{
    int a = 5;
    int b = 8;
    printf ( " Before swapping a = %d , b = %d\n",a,b);
    swap( a , b);
    printf ( " After calling swap function a = %d , b = %d\n",a,b);
}
swap( p , q)
int p , q;
{
    int temp;
    temp = p;
    p = q;
    q = temp;
    printf ( " In swapping function  p = %d , q = %d\n",p,q);
}