Program to interchange the value of variables from call by reference

/* program to interchange the value of variables from call by reference */
#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);
}