The Best Guide to Understand C++ Header Files

Different languages have various predefined functions which help in writing and managing a program. Similarly, in C++, various header files play an essential part in C++ programming, and it helps to facilitate users by providing features to them while programming.

This tutorial on C++ Header files will help you learn all about Header files.

Why Do You Use Header Files?

Header files are used in C++ so that you don’t have to write the code for every single thing. It helps to reduce the complexity and number of lines of code. It also gives you the benefit of reusing the functions that are declared in header files to different .cpp files and including a header file is way easier than writing the implementations. By using a header file, you keep the program precise and focused, which makes it manageable.

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What Are C++ Header Files?

These are those files that store predefined functions. It contains definitions of functions that you can include or import using a preprocessor directive #include. This preprocessor directive tells the compiler that the header file needs to be processed prior to the compilation. For example, the <iostream> header file in C++ contains the definition of input-output functions.




Here, iomanip is the name of the header file, and .h is the extension of the header file. Unlike C, C++ header files may or may not have .h extension. It must enclose the name of the header file in the angle brackets, and #include is the preprocessor directive.


Here, the name of the header file is enclosed in double quotes, and this syntax is usually preferred when you are defining a user-defined header file.

And now, you will look at the types of header files.

Types of Header Files

  • Standard library header files
  • User-defined header files

Standard library header files: These are those header files that are already present in the compiler of C++; you just need to import them to use them.

User-defined header files: These are those header files defined by the user and can be used by including them in the program using #include.

Now, understand how these header files work.

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How Do Header Files Work?

When you include a header file, suppose #include<FileName.h> in the program, it provides information to the compiler that it possesses this function and its functionality, and the compiler directly replaces the <FileName.h> with its actual functionality or its content. Thus, you don’t have to write the code for it because you have already imported the header file, and it has all the information that the compiler needs to know. 

How to Create a Header File in C++?

In C++, the code gets bigger and bigger with the functionality, and if you are working on some project, it would not be easy to manage and analyze the complete code of the project. So to avoid this problem, you can create your header file, and can use it whenever you require.

First of all, create a header file, and for that, you will write your code in the file, and save it with the .h extension, for example, fname.h. Here, you are using the .h extension because you are naming a header file.


The above code is of the header file fname.h 

Now open a new file and write the code; for example, here, you have written the code to find the average of three numbers, but you haven’t written the logic for it. Instead of writing the code, you must simply add the header file, i.e., fname.h, using #include and double-quotes. Then, you must save it with the .cpp extension. 


After saving the file, run the code, and below is the output of the code, i.e., the average of three numbers.


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After reading this tutorial on C++ Header files, you would have understood why you use Header files, what C++ Header files are, their syntax, and the types of Header files in C++. You also learned about the working of C++ Header files and how you can create your header file with the help of some examples.

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Do you have any questions regarding this tutorial on C++ Header files? If you do, then please put them in the comments section. We’ll help you solve your queries. To learn more about C++ Header files, click on the following link: C++ Header files

Happy learning!

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Kartik MenonKartik Menon

Kartik is an experienced content strategist and an accomplished technology marketing specialist passionate about designing engaging user experiences with integrated marketing and communication solutions.

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