#define MOTORS (*(char *)0x1004)
int main()
{
    register short int x; // 16 bit register
    register char a;      //  8 bit register
    
    a = 0xf0;             // put a value in a that would turn on the lights

    while (1) {
        MOTORS = a;       // write out to motors

        for (x = 0xffff; x != 0; x--) { /* wait */ }

        a = a ^ 0xf;      // reverse the lights' color
    }
}