main

#include <REGX52.H>
#include "Delay.h"
#include "Nixie.h"

void main()
{
    while(1)
    {
        Nixie(1,1);
        Nixie(2,2);
        Nixie(3,3);
        Nixie(4,4);
        Nixie(5,5);
        Nixie(6,6);
    }
}

Delay .c 

void Delay(unsigned int xms)
    //@12.000MHz
{
    unsigned char data i, j;
  while(xms--)
    {
        i = 2;
        j = 239;
        do
        {
            while (--j);
        } while (--i);
    }
    
}

Delay .h

#ifndef __DELAY_H__
#define __DELAY_H__

void Delay(unsigned int xms);
    
#endif

Nixie .c 

#include <REGX52.H>
#include "Delay.h"

unsigned char NixieTable[]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F};

void Nixie(unsigned char Location,Number)
{
    switch(Location)
        {
            case 1:P2_4=1;P2_3=1;P2_2=1;break;
            case 2:P2_4=1;P2_3=1;P2_2=0;break;
            case 3:P2_4=1;P2_3=0;P2_2=1;break;
            case 4:P2_4=1;P2_3=0;P2_2=0;break;
            case 5:P2_4=0;P2_3=1;P2_2=1;break;
            case 6:P2_4=0;P2_3=1;P2_2=0;break;
            case 7:P2_4=0;P2_3=0;P2_2=1;break;
            case 8:P2_4=0;P2_3=0;P2_2=0;break;
        }
        P0=NixieTable[Number];
        Delay(1);
        P0=0x00;
}

Nixie .h

#ifndef __Nixie_H__
#define __Nixie_H__

void Nixie(unsigned char Location,Number);

#endif