#define ddrb 0x37;
#define portb 0x38;

void led_on()
{
    char* led = portb;
    *led = 0xff;
}

void led_off()
{
    char* led = portb;
    *led = 0x00;
}

int main(void) {
    int i;
    char* io_dir = ddrb;
    *io_dir = 0xff;
    while(1) {
        led_on();
        for(i = 0; i < 0xffff; i++);
        led_off();
	for(i = 0; i < 0xffff; i++);
    }
    return 0;
}