Creating header file

Can you please tell me the step wise process to create the header file .
Also tell me where to create this header file, in the notepad or in the keil software itself with in the program.
I want to create header file for the following errors:
lcd.h
rtc.h
bcd2ascii.h
serial.h
For the following program.:-

#include<reg52.h>
#include <lcd.h>
#include <rtc.h>
#include<string.h>
#include<bcd2ascii.h>
#include<serial.h>

sbit sw1=P3^7;
sbit sw2=P3^6;
sbit sw3=P3^5;
sbit buzzer=P2^3;
sbit relay=P2^2;
sbit rled =P3^4;
sbit gled =P3^3;
bit flag_sw,flagr=0;

static unsigned char k=0,s=0x84,*result,h,unit=0;
unsigned char inc=23,check_flag=0,month_flag=0,month;
unsigned char *time,*res;
unsigned char idata byte1[100];
unsigned char *date,*u,i,j,a=0,b,c,d;

void main()
{ TMOD=0x20; // serial communication intialization
TH1=0XFD;SCON=0X50;TR1=1;i=0;
IE=0X91;IT0=0;

lcdInit(); // LCD intialization
LCDstr("AUTOMATIC POWER",0x80);
LCDstr("METER READING",0xc0);
delay(2000);

gsm_check();gsm_rec(); //gsm modem intialization
gled=0;rled=1;buzzer=1;relay=1;

while(1) //super loop
{

//time display
LCDstr("DATE ",0x80);
LCDstr("TIME",0xc0);
date=getDate();
LCDstr(date,0x86);
time=getTime();
LCDstr(time,0xc6);
flag_sw=0;delay(1000);

//units display
putComL(0x01);
LCDstr("UNITS=",0x80);
putComL(0x86);
unit=getCharE(0x15);
u=bcdtoascii(unit);
LCDstr(u,0x87);

delay(2000);

/**************checking********************/

a=getCharE(0x04); // gsm modem sending sms
if(a>=28 )
{ gsm_check();
delay(200);
ES=0;
unit=0;
putCharE(unit,0x15);
rled=0;gled=1;
gsm_send(byte,"number"); }

//else case
..
if(a>=16 & d==c){month_flag=1;}
else month_flag=0;month_flag=getCharE(0x20);

if(check_flag==0 & month_flag==1 &flagr==0){flagr=1;relay=0;rled=0;gled=1;buzzer=0;delay(100);buzzer=1;}
else if(check_flag==1 ){ gled=0;rled=1;buzzer=1;relay=1;} delay(1000);

//receving sms
for(j=0;j<100;j++) {if(byte1[j]=='*' &byte1[j+1]=='P' & byte1[j+2]=='A'& byte1[j+3]=='I'& byte1[j+4]=='D') {ES=0;LCDstr("received",0xc0); a=1;check_flag=1;putCharE(check_flag,0x10); gsm_rec(); }} //time setting

if(sw3==0){enter_time();}
delay(1000);k=0;

}}

Please also tell me whether the program is correct or not..
please Guide me