说明：  设计一个简易数字钟，具有校时功能： 1、以至少6位LED数码管显示时、分、秒，时为24进制。 2、采用最多8个键实现校时功能。
(The design of a simple digital clock with a school function: 1, to at least six LED digital display hours, minutes and seconds, time for the 24-band. 2, using up to eight key functions to achieve school.)