PIC 16F877A 4 Seven Segment counter Not counting

#include "Display_utils.h"

char kraj;
unsigned short zz, j, v;
unsigned int i;
unsigned short por[4];

void interrupt() {
  PORTA = 0;
  PORTD = por[v];
  PORTA = zz;              // turn on appropriate 7seg. display
  zz <<= 1;
  if (zz > 8u)
    zz = 1;                // prepare mask for digit
    
  v++ ;
  if (v > 3u)
    v = 0;                 // turn on 1st, turn off 2nd 7seg.
    
  TMR0   =   0;
  INTCON = 0x20;
}//~

void main() {
  OPTION_REG = 0x80;
  j          =   0;
  v          =   0;
  zz         =   1;
  TMR0       =   0;
  INTCON     = 0xA0;       // Disable PEIE,INTE,RBIE,T0IE
  PORTA      =   0;
  TRISA      =   0;
  PORTD      =   0;
  TRISD      =   0;
  
  i          =   1989;
  do {
    j = i / 1000u ;        // prepare digits for diplays
    kraj = mask(j);
    por[3] = kraj;
    j = (char)(i / 100u) % 10u;
    kraj = mask(j);
    por[2] = kraj;
    j = (char)(i / 10u) % 10u;
    kraj = mask(j);
    por[1] = kraj;
    j = i % 10u;
    kraj = mask(j);
    por[0] = kraj;
    
    Delay_ms(1000);
    
    i++ ;                  // increment counter
    if (i > 9999u)
      i = 0;

  } while(1);              // endless loop
}//~