通过2CH、2AH号功能调用系统时间和日期，并将其显示在屏幕上；通过在主程序中判别从键盘输入的字符，实现不同的功能：结束程序、设置时间、显示秒表；在整个功能实现过程中，多次调用宏KEY、DELAY、PUSHA、POPA以减少程序代码。

-By 2CH, 2AH number call system time and date functions, and displays on the screen　by the main program in the identification of characters from the keyboard input, to achieve different functions: the end of procedure, set time, display stopwatch　in the function realization process, repeatedly calling the macro KEY, DELAY, PUSHA, POPA to reduce the program code.