car.c

#include <reg52.h>

/* 这两个貌似没用？ */
/* #define uint unsigned int */
/* #define uchar unsigned char */

#define FORWARD  1
#define STOP     0
#define BACKWARD 0

sbit backward_signal     = P3^7;
sbit forward_signal      = P3^1;
sbit intersection_signal = P3^2;
sbit traffic_signal      = P3^3;

int status = STOP;

void forward()  { P1 = 0xf0; }
void stop()     { P1 = 0xff; }
void backward() { P1 = 0x0f; }

void keep_going() {
    if(status == FORWARD)
        forward();
    else
        backward();
}

void main() {
    while(1) {
        if(!forward_signal)
            status = FORWARD;

        if(!backward_signal)
            status = BACKWARD;

        if(!intersection_signal) {
            if(traffic_signal)
                keep_going();
            else
                stop();
        }
    }
}