LCD in 4bit MODE -8051

/* LCD 4bit MODE-  D7-D4 of LCD are connected to P2.7-P2.4

   ALGORITHM- first higher byte is sent and then the lower byte
          
     step1: mask the Lower nibble and send them to LCD 
               (temp= value & 0xf0);
          send(temp);
     step2: enable pulse
     step3: left shift the value for 4 times, which makes lower nibble
            moves to higher nibble and higher nibble moves to lower nibble
          temp= value<<4;
       temp=value & 0xf0;
       send(temp);
     step4: enable pulse      */


#include<reg51.h>

void delay_msec(int);
void lcd_init();
void lcd_data(char);
void send(char);
void lcd_cmd(char);
void lcd_dataS(char *p);
void lcd_data_int(int);

sbit rs=P2^0;
sbit en=P2^1;

//***********************************------
void main()
{
  P2=0x00;
  rs=en=0;
  lcd_init();
  lcd_dataS("hello pc");
  lcd_cmd(0xc0);
  lcd_data_int(555);
  while(1)
  {
  }
}

//*************************************


void lcd_init()
{    
 delay_msec(20);
 send(0x30);   
 delay_msec(10);  
 send(0x30);
 delay_msec(1);
 send(0x30);
 delay_msec(1); 
 send(0x20);
 delay_msec(1); // upto here we call it as RESETting of LCD, 
                // and telling the LCD that we are using 4bit mode

 lcd_cmd(0x06);
 lcd_cmd(0x01);
 lcd_cmd(0x28);
 lcd_cmd(0x0e);
}

void send(char value)
{
char temp;
 temp= P2 & 0x0f; //store the higher nibble of P2 in temp
 P2= temp | value;  //now bitwise OR the value with temp,
            //which successfully sends data(higher nibble) to P2 without 
            //effecting its prevoius data in the lower nibble
 en=1;
 delay_msec(1);
 en=0;
}


void lcd_cmd(char cmd)
{
 char temp;
 temp=cmd &0xf0; //masks (makes zero) the lower nibble
 rs=0;
 send(temp);  //now send the higher nibble
 temp=cmd<<4;    //now left shift 4 times which shifts lower
          //nibble to higher nibble
 temp=temp&0xf0;  //now mask lower nibble again
 send(temp);   //and send to the LCD
}


void lcd_data(char d)
{
 char temp;
 temp=d &0xf0;
 rs=1;
 send(temp);
 temp=d<<4;
 temp=temp&0xf0;
 send(temp);
}


void lcd_dataS(char *p)
{
  char temp;
  while(*p!='\0')
  { 
    rs=1;
 temp=(*p) & 0xf0;
 send(temp);
 temp=(*p) << 4;
 temp=temp & 0xf0;
 send(temp);
 p=p+1;
  }
}

void lcd_data_int(int value)
{
  int a[3]={0,0,0},i=0,temp;
  while((value/10)!=0)
  {
   a[i]=48+value%10;
   i++;
   value=value/10;
  }
  a[i]=48+value;

  for(i=2;i>=0;i--)
  {
    rs=1;
 temp= a[i] & 0xf0;
 send(temp);
 temp=(a[i] << 4) & 0xf0;
 send(temp);
  }
}

void delay_msec(int n)
{
 int i,j;
 for(j=0;j<n;j++)
 for(i=0;i<921;i++);
}