说明：  用并行芯片8255实现抢答器，空格键清除，并且有人抢答，计算机蜂鸣器会响起，并显示组号，经过8255实际芯片测试
(Parallel chip to achieve Responder 8255, the space key to remove, and it was to answer in the computer buzzer will be sounded, and displays the group number, after 8255 the actual chip testing)