Program to explain call by reference

/* program to explain call by reference */
#include<stdio.h>
main ( )
{
    int a = 5;
    int b = 8;
    printf (" Before calling the function a and b are %d , %d\n",a,b);
    ref ( &a , &b);
    printf ( " After calling the function a and b are %d , %d\n",a,b);
}

ref ( p , q )
int *p,*q;
{
    (*p)++;
    (*q)++;
    printf ( " In function changes are %d , %d\n" , *p,*q);
}