Hiển thị số 0000-9999 lên led 7 thanh

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#include <REGX52.H>
#include<stdio.h>
#include<math.h>
sbit led1= P1^0;
sbit led2= P1^1;
sbit led3= P1^2;
sbit led4= P1^3;
unsigned char m[10]= {0xC0,0xF9,0xA4,0xB0,0x99,0x92,0x82,0xF8,0x80,0x90};
unsigned char donvi,chuc,tram,nghin;

int num;
void delay(int time)
{
while(time--);
}

void sang(unsigned int num)
{
  int i;
//num=9876;
nghin=num/1000;
tram=(num%1000)/100;
chuc=((num%1000)%100)/10;
donvi=((num%1000)%100)%10;
for(i=0;i<50;i++)
{
P2=m[nghin];
led1=1; led2=led3=led4=0;
delay(100);

P2=0xff;
delay(100);

P2=m[tram];
led2=1; led1=led3=led4=0;
delay(100);

P2=0xff;
delay(100);

P2=m[chuc];
led3=1; led1=led2=led4=0;
delay(100);

P2=0xff;
delay(100);

P2=m[donvi];
led4=1; led1=led3=led2=0;
delay(100);

P2=0xff;
delay(100);
}
}
void main()
{
while(1)
{
int n;
for(n=0;n<9999;n++)
{
sang(n);
}
}
}