Dear friend, this is the group of C # But I'll explain you
The header files whose extensions are usually h. Are only local to introduce the functions used in other codes. The advantage of the header files is that you can use them to put your own code in different files, which can be categorized as a topic or any other arbitrary category. Then it's easy to use a header file using the include command in your main project file (the main file is the file that has the main function)