#include <stdio.h>

int main(void)
{

  int p, q; 

  p = 0x55;
  printf("p=%x (original)\n", p);

  p &= 0x0f;
  printf("p=%x (&=0x0f)\n", p);

  p = 0x55;
  p |= 0x0f;
  printf("p=%x (|=0x0f)\n", p);

  p = 0x55;
  p ^= 0x0f;
  printf("p=%x (^=0x0f)\n", p);

  p = 0x78; q = 0x53;
  p ^= q;
  p ^= q;
  printf("p=%x (p^=q, p^=q)\n", p);
 
  return 0;
}