Eight bit responder [51 single chip microcomputer]

Design purpose ： Design an eight way responder , The rush time is 30S count down , After grabbing it , Yes 10S Time to answer questions

#include <reg52.h>
#include <absacc.h>
unsigned char code SEG[10]={
    0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};// Broken code table of digital tube , Common Yin level 
unsigned char dispbuf[2]={
    0,0};  // Display 100 bits of buffer 
unsigned char flag=0; //1s To the flag 
sbit setting=P3^0;
sbit opening=P3^1;
sbit beep=P3^7;
unsigned char number;// Store the key answering number 
unsigned char m;
unsigned char mm=30;// Store answers 30 second 
/*  Timer initialization function  @  Peng Wangchong  */
void delay();
void display(unsigned char m);
unsigned char anjian();// Function declaration 
void Timer0_Init()		  
{
      TMOD=0x01;  // Timer 0 The way 1
   TH0=(65536-5000)/256;    // timing 5ms
   TL0=(65536-5000)%256;
   ET0=1;	   // Open the interrupt 
   EA=1;
   TR0=1; 	 // Turn on the timer 0
}
void Timer0_ISR()  interrupt 1 using 0
{
      
   static unsigned char i=0,k=0;// among m and mm Respectively 5 Second countdown and 30 Second countdown 
   
   TH0=(65536-5000)/256; // Reset the initial value 
   TL0=(65536-5000)%256;
	 k++;
  if(k==200)  
  {
     
      k=0;
		if(mm==0)
		   mm=0;
		else
	    mm--;
		 
		
  }
	if(mm==3)
	{
    for(m=3;m--;m>0)
		
		{
    beep=!beep;
		delay();}
	}
		
	P1=0xff;// Turn off the nixie tube 
	if(i==2)
		P1=SEG[number];
	else
		P1=SEG[dispbuf[i]];
	  P3 = ~(0x08<<i);
	i++;
	if(i==3)
		i=0;
 display(mm);
 
}
void display(unsigned char m)
{
    
     dispbuf[1]= m/10      ;	// Get ten 
	   dispbuf[0]= m%10       ;	// Get bits  
}
// Salt water 
void delay()
{
      unsigned char i;
   for(i=0;i<120;i++);	   // Time delay 1ms
}


void main()
{
     
	
	Timer0_Init();
		
	while(1)
	{
      if(opening==0)
			mm=30;
		if(P2!=0xff)// If a key is pressed , Then return the key value 
		{
    
			
			number=anjian();
			mm=10;
			while(1)
			{
    
				if(opening==0)
				{
    mm=30;number=0;break;}
			}
		
		}
		
	
	}
}
// Case handling function 
unsigned char anjian()
{
    
	switch(P2)
	{
    
		case 0xfe:return 1;break;
		case 0xfd:return 2;break;
		case 0xfb:return 3;break;
		case 0xf7:return 4;break;
		case 0xef:return 5;break;
		case 0xdf:return 6;break;
		case 0xbf:return 7;break;
		case 0x7f:return 8;break;
	   default:return 0;
	}
}