#include <stdio.h>

void swap_val(int x, int y)
{
    int temp;

    temp = x;
    x = y;
    y = temp;
}

void swap_ref(int *px, int *py)
{
    int temp;

    temp = *px;
    *px = *py;
    *py = temp;
}

int main(void)
{
    int a = 5, b = 9;

    swap_val(a, b);
    printf("%d %d\n", a, b);

    swap_ref(&a, &b);
    printf("%d %d\n", a, b);

    return 0;
}