#include <stdio.h>
#define SWAP(a,b,c) c t;t=*a;*a=*b;*b=t;

int main(void)
{
   int x=10,y=20;
   printf("Before swapping\n");
   printf("%d %d\n",x,y);
   SWAP(&x,&y,int);
   printf("After swapping\n");
   printf("%d %d\n",x,y);
   return 0;
}