数码管可以显示0-999三位数字，按一下加按键，数字加1；按一下减按键，数字减1。初始化显示为学号后三位。提交C文件

#include <reg52.h>

#define uchar unsigned char
#define uint unsigned int

sbit keyAdd = P3 ^ 1;
sbit keySub = P3 ^ 0;
sbit dula = P2 ^ 6;
sbit wela = P2 ^ 7;

uchar code segCode[] = {0x3f, 0x06, 0x5b, 0x4f, 0x66, 0x6d, 0x7d, 0x07, 0x7f, 0x6f};

uchar cnt = 0;
uchar num[3] = {0, 1, 6};

void delay(uint i)
{
    while (i--)
        ;
}

void display()
{
    uchar i;
    for (i = 0; i < 3; i++)
    {
        wela = 1 << i;
        P0 = segCode[num[i]];
        delay(1000);
        P0 = 0x00;
        wela = 0x00;
        dula = 1;
        dula = 0;
    }
}

void keyScan()
{
    if (keyAdd == 0)
    {
        delay(10);
        if (keyAdd == 0)
        {
            cnt++;
            if (cnt > 999)
            {
                cnt = 0;
            }
            num[0] = cnt / 100;
            num[1] = cnt / 10 % 10;
            num[2] = cnt % 10;
            display();
        }
        while (!keyAdd)
            ;
    }
    if (keySub == 0)
    {
        delay(10);
        if (keySub == 0)
        {
            cnt--;
            if (cnt < 0)
            {
                cnt = 999;
            }
            num[0] = cnt / 100;
            num[1] = cnt / 10 % 10;
            num[2] = cnt % 10;
            display();
        }
        while (!keySub)
            ;
    }
}

void main()
{
    display();
    while (1)
    {
        keyScan();
    }
}