通过按下K0，K1，K2，K3四个不同的键来控制LED发光二级管的显示规律。(哈工大单片机大作业内附proteus原理图)-By pressing K0, K1, K2, K3 are four different keys to control the regularity of the LED light emitting diode display. (HIT SCM operations included proteus diagram)