microcontroller AT89S52 programing advice

#include <reg51.h>
#include <stdio.h>

> im required to make a digital clock , i made several codes using
> iteration for delay which give not perfect delay. So i want to have
> suggestion about how to use timer interrupts to have perfect 1 sec
> delay each time. ive written code please see am i using interrupts
> correctly..
<snip code>

> im required to make a digital clock , i made several codes using
> iteration for delay which give not perfect delay. So i want to have
> suggestion about how to use timer interrupts to have perfect 1 sec
> delay each time. ive written code please see am i using interrupts
> correctly..
>
> unsigned char
> LED[10]=;
> unsigned char AMPM[2]=;
> long int
> x,sec=0,min=0,hour=0,lmin=0,hmin=0,c=0;hhour=0,lhour=0,le=0,am=0;
> sbit a=P3^0;
> sbit b=P3^1;
> sbit d=P3^4;
> sbit e=P3^7;
> sbit f=P3^6;
> void init_timer()
> {
> ET1=1;
> TMOD=0x20;
> TH1=0x6;
> EA=1;
> TR1=1;
> }
>
> timer1() interrupt 3
> {
> hmin=min/10;
> lmin=min%10;
> hhour=hour/10;
> lhour=hour%10;
>      while(c<@00)
>      {
>      le++;
>      c++;
>      switch(le)
> {
> case 1:
> a=0;
> b=1;
> d=1;
> e=1;
>             f=1;
>          P0=~LED[hhour];
>             break;
>
>          case 2:
> a=1;
>             b=0;
>             d=1;
>             e=1;
>             f=1;
>             P0=~LED[lhour];
>             break;
>
>          case 3:
>             a=1;
>             b=1;
>             d=0;
>             e=1;
>             f=1;
>             P0=~LED[hmin];
>             break;
>
>          case 4:
>             a=1;
>             b=1;
>             d=1;
>             e=0;
>             f=1;
>             P0=~LED[lmin];
>             break;
>          case 5:
>          a=1;
>             b=1;
>             d=1;
>             e=1;
>             f=0;
>             P0=~AMPM[am];
>             le=0;
>             break;
>      }
>      }c=0;
>      sec++;
>      if(sec=`)
>      {sec=0;
>      min++;
>      }
>      if(min=`)
>      {min=0;
>      hour++;
>      }
>
> }
> main()
> {
>
> EA=1;
> am=0;
> le=0;
> sec = 0;
> min = 0;
> hour= 0;
> c=0;    
> init_timer();
> for(;;)
> {}
> }
>

>im required to make a digital clock , i made several codes using
>iteration for delay which give not perfect delay. So i want to have
>suggestion about how to use timer interrupts to have perfect 1 sec
>delay each time. ive written code please see am i using interrupts
>correctly..

>timer1() interrupt 3
>{
>hmin=min/10;
>lmin=min%10;
>hhour=hour/10;
>lhour=hour%10;
>     while(c<@00)
>     {
>     le++;
>     c++;
>     switch(le)

if(int_count>=NUMBER_OF_INTS_PER_SECOND)

if(sec_counter>`)