Header Files in C

In C programming, header files play a crucial role. A header file is a file that contains necessary information like function declarations, macro definitions, constants, and structures. It is included in other parts of the program so that its contents can be used. Header files primarily serve to organize and manage code that needs to be reused.

They provide code reusability, code organization, forward declaration, and portability.

Header files are included in a C program using the `#include` directive. There are two ways to do this:

System Header Files: Included with angle brackets `<>`, e.g., `#include `.

User-Defined Header Files: Included with double quotes `""`, e.g., `#include "myheader.h"`.

The document lists and explains major standard library header files like `stdio.h` (Standard Input/Output), `stdlib.h` (Standard Library for memory allocation, etc.), `string.h` (String Handling), `math.h` (Mathematical Functions), `ctype.h` (Character Handling), and `time.h` (Time Functions), with examples for each.

The text explains how to create your own header files to define your own functions, macros, and structures for reuse across different programs.

The main problem is the "Multiple Inclusion Problem," which can lead to multiple definition errors. This is solved using "include guards" (`#ifndef`, `#define`, `#endif`) to ensure a header file is included only once.