Time Display On LCD using 8051 Microcontroller

/* Displaying time on LCD using microcontroller
    To get 1sec delay timer(16bit mode) should overflow 14 times, 
 but instead i have used only 11 times because I 
 have counted prograam instructions delays and 11 
 times will increment exactly 1sec.   

 algorithm: wait in the loop for INCREMENT to be 1
      INCREMENT will be 1 only when the timer0
      overflows for 11 times(spcifically for my program)
      see my program logic, you can understand  */


#include<reg51.h>
#include "lcd_display4bit.h"

sbit ON=P1^0;
sbit SET=P1^1;
sbit incr_hrs=P1^2;
sbit incr_min=P1^3;
sbit set_hrs=P1^5;
sbit set_min=P1^4;

int sec,min,hrs;
int min_value=0,hrs_value=0,sec_value=0;
int count=0,increment=0;

void timer0() interrupt 1
{

  EA=0;
   TH0=0x00;
   TL0=0x00;
   count++;       //everytime timer overflows count is incremented
   if(count==11)  //if count is 11 then make increment=1
    {             //why 11 because if timer overflows for 11 times  
     count=0;     //then it will be 1sec
     increment=1;
    }
 else 
  increment=0;
  TF0=0;
  EA=1;
}

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)
  {
  }
}

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

Calculator Project with just keypad and LCD 8051

/* calculator Project for 8051---
   Possible Operation- add, sub, mul, div
   limitations- decimal part is truncated
                result upto only 6decimals */
/* algorithm::
     step1:store the entered values in an array
         if any operator key is pressed goto step2
  step2:store the var1 here (using convertArrayToDecimal() function)
        and also store the operator pressed
         if '=' operator is pressed goto step3
  step3:do the respective operation and display the result */

#include<reg51.h>
#include"lcd_display.h"

int pow(int, int);
void convertArrayToDecimal(int*);
void clear_array();
void column1();
void column2();
void column3();
void column4();
char getkey();

sbit c1=P2^0;
sbit c2=P2^1;
sbit c3=P2^2;
sbit c4=P2^3;
sbit r1=P2^4;
sbit r2=P2^5;
sbit r3=P2^6;
sbit r4=P2^7;


int var1=0,var2=0,dummy_var,row,col;

char values[4][4]={{55,56,57,'/'},
                   {52,53,54,'*'},
          {49,50,51,'-'},
          {' ',48,'=','+'}};

int num[5]; // to store the entered keys
int i=0;
void main()
{
char key;
unsigned char operation;
int var_count=0;
int result;

Security Door project Program for 8051

#include<reg51.h>
#include"lcd_display.h"

void column1();
void column2();
void column3();
void resetPassword();
void getNewPassword();
char getkey();

sbit c1=P0^0;
sbit c2=P0^1;
sbit c3=P0^2;
sbit r1=P0^3;
sbit r2=P0^4;
sbit r3=P0^5;
sbit r4=P0^6;
sbit reset_password=P1^2;
sbit ON=P1^3;

char reset_code[3]={'9','9','9'},password[6];

int i=0,count=0,danger=0;
int col,row;
char num[4][3]={{'1','2','3'},
                {'4','5','6'},
       {'7','8','9'},
       {'*','0','#'}};

void main()
{
  char c;
  c1=c2=c2=1;
  r1=r2=r3=r4=0;
  reset_password=ON=1;
  rs=en=0;
  P2=0x00;
  TMOD=0x01;
  lcd_init();