用数码管的前两位显示一个十进制数，变化范围为00-59,开始时显示00

//用数码管的前两位显示一个十进制数，变化范围为00-59,开始时显示00，每按下S2键一次，数值加1，每按下S3，数值减1，每按下S4，数值归零，每按下S5
//功能开始自动加1，再次按下S5，数值停止自动加1，保持显示原数。

#include<reg52.h>
#define uchar unsigned char
#define uint unsigned int

sbit key1=P3^4;
sbit key2=P3^5;
sbit key3=P3^6;
sbit key4=P3^7;
sbit dula=P2^6;
sbit wela=P2^7;

uchar code table[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};
uchar numt0,num;

void delayms(uint);
void display(uchar numdis);
void init();
void keyscan();

int main()
{
    init();
    while(1)
    {
        keyscan();
        display(num);
    }
    return 0;
}

void display(uchar numdis)
{
    uchar shi,ge;
    shi=numdis/10;
    ge=numdis%10;

    dula=1;
    P0=table[shi];
    dula=0;

    P0=0xff;

    wela=1;
    P0=0xfe;
    wela=0;
    delayms(5);

    dula=1;
    P0=table[ge];
    dula=0;

    P0=0xff;

    wela=1;
    P0=0xfd;
    wela=0;
    delayms(5);
}

void delayms(uint xms)
{
    uint i,j;
    for(i=xms;i>0;i--)
        for(j=124;j>0;j--);
}

void init()
{
    TMOD=0x01;
    TH1=(65535-45872)/256;
    TL1=(65535-45872)%256;
    EA=1;
    ET0=1;
}

void keyscan()
{
    if(key1==0)
    {
        delayms(10);
        if(key1==0)
        {
            num++;
            if(num==60)
                num=0;
            while(!key1);//等待key1释放
        }
    }

    if(key2==0)
    {
        delayms(10);
        if(key2==0)
        {
            num--;
            if(num==60)
                num=0;
            while(!key2);//等待key2释放
        }
    }

    if(key3==0)
    {
        delayms(10);
        if(key3==0)
        {
            num=0;
            while(!key3);
        }
    }

    if(key4==0)
    {
        delayms(10);
        if(key4==0)
        {
            while(!key4)
                TR0=~TR0;//启动和停止定时器0
        }
    }
}

void T0_time() interrupt 1
{
    TH1=(65535-45872)/256;
    TL1=(65535-45872)%256;
    numt0++;
    if(numt0==20)
    {
        numt0=0;
        num++;
        if(num==60)
            num=0;
    }
}