用汇编语言实现的倒计时器，利用1C中断每秒中断约18次的特性，在根据中断次数计算时间，每过一秒，时间以十进制显示在屏幕上，时间减到零时程序退出。-Using assembly language implementation of the countdown device, using 1C interrupted about 18 times per second interruption characteristics, in accordance with interruptions computation time, with every passing second, the time displayed on the screen in decimal, the time reduced to zero to quit.