#include <stdio.h>

int main(void) {
    unsigned val;
    val = 0;
    printf("start: %x\n", val);
    val |= 1;
    printf("1 on: %x\n", val);
    val |= 1;
    printf("1 on: %x\n", val);
    val ^= 1;
    printf("1 off: %x\n", val);
    val ^= 1;
    printf("1 off: %x\n", val);
    return 0;
}

start: 0
1 on: 1
1 on: 1
1 off: 0
1 off: 1