嵌入式开发一：很好的数字钟程序

#include <AT89X51.H>
unsigned char code dispcode[]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F,0x40};//0123456789不亮
unsigned char dispbitcode[]={0xfe,0xfd,0xfb,0xf7,0xef,0xdf,0xbf,0x7f};//选择不同位进行点亮
unsigned char dispbuf[8]={0,0,10,0,0,10,0,0};//初值
unsigned char dispbitcnt;
unsigned char second;
unsigned char minite;
unsigned char hour;
unsigned int tcnt;
unsigned char mstcnt;
unsigned char i,j;
void main(void)
{
TMOD=0x02;
TH0=0x06;
TL0=0x06;
TR0=1;
ET0=1;//T0中断控制位
EA=1;//计数250次
while(1)
{
if(P0_0==0)
{
for(i=5;i>0;i--)
for(j=248;j>0;j--);
if(P0_0==0)
{
second++;
if(second==60)
{
second=0;
}
dispbuf[0]=second%10;
dispbuf[1]=second/10;//显示秒钟
while(P0_0==0);//表示P0_0被按下则继续执行否则跳过
}}
if(P0_1==0)
{
for(i=5;i>0;i--)
for(j=248;j>0;j--);
if(P0_1==0)
{
minite++;
if(minite==60)
{
minite=0;
}
dispbuf[3]=minite%10;
dispbuf[4]=minite/10;
while(P0_1==0);
}
}
if(P0_2==0)
{
for(i=5;i>0;i--)
for(j=248;j>0;j--);
if(P0_2==0)
{
hour++;
if(hour==24)
{hour=0;}
dispbuf[6]=hour%10;
dispbuf[7]=hour/10;
while(P0_2==0);
}}}}
void t0(void) interrupt 1 using 0//中断入口
{
mstcnt++;、
if(mstcnt==8)//2毫秒、、刷新率
{
mstcnt=0;
P1=dispcode[dispbuf[dispbitcnt]];
P3=dispbitcode[dispbitcnt];
dispbitcnt++;
if(dispbitcnt==8)//2毫秒
{
dispbitcnt=0;
}
}
tcnt++;
if(tcnt==4000)//一秒
{
tcnt=0;
second++;
if(second==60)
{
second=0;
minite++;
if(minite==60)
{
minite=0;
hour++;
if(hour==24)
{
hour=0;
}
}
}
dispbuf[0]=second%10;
dispbuf[1]=second/10;
dispbuf[3]=minite%10;
dispbuf[4]=minite/10;
dispbuf[6]=hour%10;
dispbuf[7]=hour/10;//显示各类数据
}
}