int play_sound (int hz, int time) { // hz(Hz), time(msec)
int tmp, i;
for (i = 0; i < hz * 2 * time / 1000; ++i) {
usleep(500*1000/hz);
tmp = inb(0x61);
tmp = (i & 1) ? tmp | 0x02 : tmp & ~0x02;
outb(tmp, 0x61);
}
outb((inb(0x61) & ~0x02), 0x61);
}