51，1602实现计算器的加减乘除基本功能，还有时钟显示，修改-51,1602 to achieve the basic functions of addition, subtraction, multiplication, and division calculator, clock display, modify

利用单片机的定时器/计数器以查询方式在单片机口线上产生连续周期性矩形波。 利用单片机的定时器/计数器以中断方式在单片机口线上产生连续周期性矩形波。-Use of single-chip timer/counter in query manner on the microcontroller mouth line to produce continuous periodic rectangular wave. Use of single-chip timer/counter interr

use at89c2051 to count number.software is keil c51.