Program to make a bidirectional visitor counter using IR sensor

// Program to make a bidirectional visitor counter using IR sensor

#include <reg51.h>
#define msec 1
unsigned int num=0;
sbit dig_ctrl_4=P1^3;  //declare the control pins of seven segments
sbit dig_ctrl_3=P1^2;
sbit dig_ctrl_2=P1^1;
sbit dig_ctrl_1=P1^0;
unsigned int digi_val[10]={0x40,0xF9,0x24,0x30,0x19,0x12,0x02,0xF8,0x00,0x10};
unsigned int dig_1,dig_2,dig_3,dig_4,test=0;
unsigned char dig_disp=0;
sbit up=P3^5;  //up pin to make counter count up
sbit down=P3^6;  //down pin to make counter count down

void init()  // to initialize the output pins and Timer0
{
up=down=1;
dig_ctrl_4 = 0;
dig_ctrl_3 = 0;
dig_ctrl_2 = 0;
dig_ctrl_1 = 0;
TMOD=0x01;
TL0=0xf6;
TH0=0xFf;
IE=0x82;
TR0=1;
}

void delay()  //To provide a small time delay
{
TMOD=0x01;
    TL0=0x36;
    TH0=0xF6;
    TR0=1;
    while(TF0==0);
    TR0=0;
    TF0=0;
}

void display() interrupt 1  // Function to display the digits on seven segment. For more details refer seven segment multiplexing.
{
TL0=0x36;
    TH0=0xf6;
P2=0xFF;
dig_ctrl_1 = dig_ctrl_3 = dig_ctrl_2 = dig_ctrl_4 = 0;
dig_disp++;
dig_disp=dig_disp%4;
switch(dig_disp)
{

  case 0:
  P2= digi_val[dig_1];
  dig_ctrl_1 = 1;
  break;

  case 1:
  P2= digi_val[dig_2];
  dig_ctrl_2 = 1;
  break;

  case 2:
  P2= digi_val[dig_3];
  dig_ctrl_3 = 1;
  break;

  case 3:
  P2= digi_val[dig_4];
  dig_ctrl_4 = 1;
  break;
}
}

void main()
{
   init();
   while(1)
   {
  if(up==0&&down==1)  //check if up pin is pressed
     {
  test++;
     num=test;
     dig_4=num%10;
  num=num/10;
     dig_3=num%10;
  num=num/10;
     dig_2=num%10;
  dig_1=num/10;
  if(test==9999)
  test=0;
  }
    if(up==1&&down==0)  //check if down pin is pressed
    {
  test--;
     num=test;
     dig_4=num%10;
  num=num/10;
     dig_3=num%10;
  num=num/10;
     dig_2=num%10;
  dig_1=num/10;
  if(test==0)
  test=9999;
  }
}
}