Código: macros.c
#include <stdio.h>
#define swap(x,y) {int tmp = x; x = y; y = tmp;}
int main()
{
int x = 10;
int y = 20;
printf("x = %d\n",x);
printf("y = %d\n",y);
swap(x,y);
printf("x = %d\n",x);
printf("y = %d\n",y);
}