程序功能：数码管显示实时时钟，1、2数码管显示分钟，3、4数码管显示小时，第3个数码管右侧圆点做秒钟记数，

1秒闪一次,小时到24时从0重新记数

学习重点:

1、数码管扫描(动态显示)

2、多模块的交互-Program features: digital display real-time clock, digital display minutes 1,2, 3,4-hour digital display, the first three seconds of digital control to do the right dot count, 1 second flash time, hours to 24 hours from the re-count 0 Points: 1, digital scanning (dynamic display) 2, multi-module interaction