设计一个能显示时分秒的实时时钟，通过数码管显示，同时设置一个手动开关可以作为修改时间的标志，另用两个开关来选择修改对象（时或分）是递增还是递减。-Design a display of accurate real-time clock, via digital display, while setting a manual switch can be used as a sign of modification time, and the other with two switches to s