设计一个数字电子秒表，该秒表具有显示功能和清零、开始计时、停止计时等功能。

设计的要求如下：

1.以0.1秒为最小单位进行显示；

2.秒表可显示0.1～9.9秒的量程；

3.该秒表具有清零、开始计时、停止计时功能；

-Sheji a digital electronic stopwatch, Gai stopwatch 具有 display and clear, start time, Tingzhi timer function. Design requirements are as follows: 1. In 0.1 seconds, the smallest unit for display　2. Stopwatch to display the range of 0.1 to 9.9 seconds　3. The stopwatch has cleared, the start time, stop the clock function