/* File: swap.c 
   -----------------------------
   Using parameter passing by reference to
   swap 2 variables
*/

#include <stdio.h>

/* Prototypes */
void swap_integers (int *, int *) ;

main() {
   int a = 1, b = 15 ;

   printf("Before swap: a = %d, b = %d\n", a, b) ;
   swap_integers (&a, &b) ;
   printf("After swap: a = %d, b = %d\n", a, b) ;
}

void swap_integers (int *ptr1, int *ptr2) {
   int temp ;

   temp = *ptr1 ;
   *ptr1 = *ptr2 ;
   *ptr2 = temp ;
}

-------------------------------------------------

Before swap: a = 1, b = 15
After swap: a = 15, b = 1