程序代码：

#include<reg51.h>
void display();
void time();



void delay10ms(unsigned char i)             //延迟函数（for循环需要时间） 当第二层for函数为p=100时（经过测量），i为多少，延迟时间就是i*10ms
{                                         //目的是在两次灯亮之间空出时间
    int n,p;
       for(n=0;n<i;n++)
           for(p=0;p<200;p++);
}

unsigned int i;
unsigned int duanma[11]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x98,0xbf};
unsigned int weima[8]={0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80};
unsigned int s1=0,s=0,m=0,h=0,number=0;
unsigned int num[8]={0,0,10,0,0,10,0,0};
unsigned int counter;

void main()
{
   
   IT0=1;    //
   IT1=1;    //下降沿触发方式
   EX0=1;  
   EX1=1;
   EA=1; 
  //以下两行为片选语句,不可以删除。否则无法操作LED
    P2 = 0xa0;P0 = 0x00;P2 = 0;    //选中蜂鸣器,关闭蜂鸣器
    P2 = 0xC0;P0 = 0xFF;P2 = 0; //位选全部选中
    P2 = 0xE0;        //选中数码管              打开Y7
      while(1)
      {      
        time();
        display();       
      }
}
void display()
{
  for(i=0;i<8;i++)
  {
    number=num[i]; 
    P2=0xC0;P0=weima[i];P2=0;
    P2=0xE0;P0=duanma[number];P2=0;
    delay10ms(1);
    P0=0xFF;   
  }
}

void time()
{
    num[7]=counter%10;
    num[6]=(counter/10)%10;
    num[5]=(counter/100)%10;
    num[4]=(counter/1000)%10;
    num[3]=(counter/10000)%10;
    num[2]=(counter/100000)%10;
    num[1]=(counter/1000000)%10;
    num[0]=(counter/10000000)%10;
}  

void interrupt_int0(void) interrupt 0          //P3.2  Pin
{   
    counter++;
}

void interrupt1_int1(void) interrupt 2         //P3.3  Pin
{   
    counter--;
}

程序代码：

    num[7]=counter%10;
    for(i=6;i<=0;i--)
    {
        num[i]=counter/pow(10,7-i);
    }