编写程序控制8255A可编程并行接口芯片，使实验台上的红、绿、黄发光二极管按照十字路*通信号灯的规律交替发光。当按下任意键则停止运行，返回DOS。-preparation process control 8255A programmable parallel interface chip, lab tables in red, green, Huang LED traffic lights in accordance with the crossroads of the law turn luminescence. When pressed Anykey will cease operation and return to DOS.