Header file in C

In C, a file with .h extension is called Header file. Header file contains function prototype(declarations) and macro definition. These header files can be included in to the other c source files to use its predefined functions or macros.

Advantages of Header file

1. Header files provide different type of functionality to perform various operations in c program, Hence reduces development time.
2. It can be used in multiple c program files, which avoids code duplicacy.

How to use/include header file

To use header file in c program, #include directive is used. All header files, should be declared at the top of c program. #include directive is used to import/include a header file into a source file.

Syntax

#include<header_file_name.h>
#include"header_file_name.h"

Example

#include<stdio.h>
#include"conio.h"

int main()
{

return 0;
}

Header files can be included in two ways.

<header_file_name.h>	within angle brackets
"header_file_name.h"	within double quotes

<header_file_name.h> within angle brackets searches header files in system directories.

"header_file_name.h" within double quotes searches header files in current directory and then system directory.

Header files are of two types

System header files	These files comes with compiler and exposes OS interfaces like IO, memory, storage etc.
User header files	A header file created by a programmer for their projects or software's to make code cleaner, easier to debug and no code duplicacy.