设计一个简单的电子秒表（按一下钮启动，再按一个停止，再按一下清零，周而复始。）最小计时单位0.01S,即可显示XX.XX（秒、百分之一秒）。-Design a simple electronic stopwatch (click Start button, and then a stop, and then click Reset again and again.) Minimum time unit 0.01S, to display XX.XX (seconds, hundredth of a second).