#include <stdio.h>

int main(void);
void swap_int1(int x,   int y);
void swap_int2(int *xp, int *yp);

void swap_int1(int x, int y) {
  int tmp;
  tmp = x;
  x = y;
  y = tmp;
}

void swap_int2(int *xp, int *yp) {
  int tmp;
  tmp = *xp;
  *xp = *yp;
  *yp = tmp;
}

int main(void) {
  int x, y;
  x = 4;
  y = 5;

  printf("値呼び出し (call by value)\n");
  printf("x=%d, y=%d\n", x, y);
  swap_int1(x, y);
  printf("x=%d, y=%d\n", x, y);

  printf("参照呼び出し(call by reference)\n");
  printf("x=%d, y=%d\n", x, y);
  swap_int2(&x, &y);
  printf("x=%d, y=%d\n", x, y);

  return 0;
}