说明：  该时钟函数包括了AT89C52、8位数码管、具有调时、闹钟等功能。所有功能的实现均使用定时器，未用时钟芯片。
(The clock function, including the AT89C52, 8 bit digital tube, with a tune, the alarm clock functions. The realization of all the features are the use of timers, not by the clock chip.)