按键key1时，数码管显示数据增加，增至100时停留显示100；按键key2数据递减，减至0时，停留显示0；按键key3时，数据清0数据停留显示为0-Keys key1, the digital tube display data to increase to $ 100 when you stay Show 100 keys key2 data decremented to 0, the residence shows 0 button key3, the data is cleared