What are Header files?

       Header file contains different predefined functions, which are required to run the program. All header files should be included explicitly before main ( ) function.Header files are also called as Pre-compiled header.

Here is some C programming header files ...

• <assert.h>
• <complex.h> 
• <ctype.h>
• <errno.h>  
• <fenv.h> 
• <float.h> 
• <graphic.h>
• <inttypes.h>
• <iso646>
• <limits.h>
• <locale.h>
• <math.h> 
• <process.h>
• <setjmp.h> 
• <signal.h>
• <stdalign.h>
• <stdatomic.h>
• <stdbool.h> 
• <stdarg.h>
• <stddef.h>
• <stdint.h> 
• <stdio.h> 
• <stdlib.h>
• <stdnoreturn.h> 
• <string.h>
• <threads.h> 
• <tgmath.h> 
• <time.h>
• <uchar.h>
• <wchar.h>
• <wctype.h>

We can input using two methods

1. #include<Header file name >
     example: #include<stdio.h>

2. #include "Header file name"
     example: #include "stdio.h"

Now you know how its included to your program, next question should be what should be written in it.as a biginner you have to just define functions in it like you do in simple c program and when you need to use that function just include that header file to your program.