How To Write Your Own Header File In C?

How To Write Your Own Header File In C?

Creating your own header files in C is an important skill that helps you organize your code better. Header files allow you to declare functions and data structures that you can use in different parts of your program. This guide will show you how to make your own header files in C, making your code easier to manage and reuse. Whether you’re working on a small project or a big one, learning this skill will make your coding life simpler.

Note:

The Header files will mostly have definitions of data types, function prototypes and C preprocessor commands.

Example to show how to create a header file

1. Creating my head.h

Write the code provided below and save it as myhead.h or enter any name along with the extension of .h which will represent a header file.

// It is not recommended to put function definitions  
// in a header file. Ideally there should be only 
// function declarations. Purpose of this code is 
// to only demonstrate working of header files. 
void add(int a, int b) 
{ 
    printf("Added value=%d\n", a + b); 
} 
void multiply(int a, int b) 
{ 
    printf("Multiplied value=%d\n", a * b); 
} 

2. Including the .h file in other programs

We have to add stdio.h as #include for using the printf () function. Additionally, we have to add the header file. h as #include”my header.h”. These “” functions to instructs the preprocessor to monitor the present folder and you can look at the standard folder when the header file is not found in the present folder. Make a note that only use “” angular bracket if the header file is saved in same folder.

3. Using the created header file

// C program to use the above created header file 
#include <stdio.h> 
#include "myhead.h" 
int main() 
{ 
    add(4, 6); 
  
    /*This calls add function written in myhead.h   
      and therefore no compilation error.*/
    multiply(5, 5); 
  
    // Same for the multiply function in myhead.h 
    printf("BYE!See you Soon"); 
    return 0; 
} 

Output

Added value:10
Multiplied value:25
BYE!See you Soon

Important Points

Header files play a crucial role in large C programs by allowing different parts of the program to share essential information like function definitions, prototypes, global variables, and structure declarations. They help centralize these declarations, making code more organized and reusable.

To create effective header files:

• Include only the minimum required statements.
• Avoid redundant or unnecessary header files.
• Don’t place function definitions in header files; save them in separate .c files.
• Include declarations for functions and variables whose definitions are meant to be shared with the linker.
• Define data structures and enumerations that are used across multiple source files.

In summary, keep header files concise and include only what’s necessary for efficient code organization and reusability.

FAQ- How To Write Your Own Header File In C?