Water level controller program

#include<reg51.h>
#include <string.h>

sbit rs = P2^0;     // defining different pins of 8051
sbit en = P2^2;
sbit rw = P2^1;
sbit wr = P3^6;
sbit rd = P3^7;
sbit led1 = P2^3;
sbit led2 = P2^4;
sbit led3 = P2^5;
sbit led4 = P2^6;
sbit led5 = P2^7;
sbit wtrin = P3^4;
sbit wtrout = P3^5;
sbit wtrstp = P3^0;
sbit limit = P3^1;
unsigned char data d;
unsigned int c=0;

void dely();     //function definations
void bigdly(int);
void lcddly();
void display(unsigned char z);
void writecmd(unsigned char a);
void writedat(unsigned char b);
void writestr(unsigned char *s);

void int1(void) interrupt 2   // external interrupt 1 subroutine
  {
 EA=0;       // disable all interrupts
 led5=1;      // read pulse indication
 rd = 0;      // send read pulse to ADC
 d=P1;         // read the data
 rd=1;
 dely();      //
 led5=0;
 writecmd(0xC0);    // display it on LCD
 writestr("cur water level:- ");
 display(d);  
 EA=1;         // enable all interrupts
   }
 void timer(void) interrupt 1 // timer overflow interrupt subroutine
   {
     EA=0;         // disable all interrupts
  c++;         // increment count
  TH0=0x3C;        // relaod timer
  TL0=0xAF;
  if(c==40)        // if count is 40
    {
      led4=1;
   dely(); 
   wr = 0;    // send write pulse to ADC
   wr = 1;
   led4=0;
   c=0;    // start countin again
  }
   EA=1;
 }
 void int0(void) interrupt 0 // external interrupt 0 subroutine
 {
  EA=0;      //disable interrupts
 led3=0;
 led1=1;
 wtrin=1;       // apply fwd puls and give indication
 dely();
 wtrin=0;
 EA=1;
  }

void display(unsigned char z)
  {
   unsigned int tmp1,tmp2,t,t1,a;
 unsigned char asci[3];
 tmp1 = (z & 0x0F);    // separate upper and lower nibbles of hex value
 tmp2 = z >> 4; 
 tmp2 = tmp2*16;     // convert it into decimal 
 t = tmp1+tmp2;
  if(t>=100)      // if its 3 digit
   {
  a=2;      // take a as 3 digit value
  while(t>10)
  {  
   t1=t%10;
   asci[a]=t1+0x30;  // convert each digit in to ASCII
   t=t/10;
   a--;
  }
  asci[0]=t+0x30;
   }
 else
   {
  t1=t%10;     // if 2 digit
  asci[2]=t1+0x30;
  t=t/10;
  asci[1]=t+0x30;
  asci[0]=0x30;    // take first digit as 0
   }
 writedat(asci[0]);    // send all 3 digits to LCD
 writedat(asci[1]);
 writedat(asci[2]);
  }
void dely()       // delay of 100 ms
  {
   int i,j;
 for(i=0;i<100;i++)
   for(j=0;j<250;j++);
   }
void bigdly(int k)      // variable delay in seconds
  {
    int i,j;
 for(i=0;i<k;i++)
   for(j=0;j<10000;j++);
  }
void lcddly()    // LCD delay
{
 int x;
 for(x=0;x<1500;x++);
 }
void writecmd(unsigned char a)
{
 lcddly();
 rs = 0;
 rw = 0;
 P0 = a; 
 en = 1; 
 en = 0;
}
void writedat(unsigned char b)
{
 lcddly();
 rs = 1;
 rw = 0;
 P0 = b;
 en = 1; 
    en = 0; 
}
void writestr(unsigned char *s)
{
 unsigned char l,i;
 l = strlen(s);      // first get the lenght of message
 for(i=1;i<l;i++)
 {
  writedat(*s);     // send all characters one by one to LCD
  s++;  
 } 
}  
main()
{
 P1=0xFF;
 P2=0x00;         // initialize ports
 P3=0xCE;
 P0=0x00; 
 IE=0x87;         // enable interrupts
 TMOD=0x01;         // initialize timer
 TH0=0x3C;         // load timer to count up to
 TL0=0xAF;          // 50,000
 writecmd(0x3C);        // initialize LCD
 writecmd(0x0F);
 writecmd(0x01);
 writestr("set water level:- ");  // display set water level as
 display(0xB4);      // 180d
 wtrin=1;           // send fwd pulse
 led1=1;           // indicate on LED
 led4=1;
 dely(); 
 wr = 0;            // send WR pulse to ADC
 wr = 1; 
 TR0=1;            // start timer
 wtrin=0;
 led4=0;
agin:while(limit==1);       // wait until set value is reached
 led1=0;
 led2=1;
 wtrstp=1;          // stop water flow
 dely();
 wtrstp=0;
 bigdly(200);          // wait for 10 sec
 led2=0;
 led3=1;
 wtrout=1;          // send rev pulse
 dely();
 wtrout=0;
 bigdly(50);          // after 2-3 sec
 limit=1;
 goto agin;          // again wait for set value reached
 }