How do I create own header files in C language

It is hard to give a detailed explanation without knowing what the header file should contain at all.

Note also the the "creation" of a header file is nothing else than the creation of a text file.

In general, header files should contain declarations (like specifying names and types) and source files should contain definitions (implementations).

A header file is usually "connected" to a source file. That means it contains the declarations for the corresponding source file. It is then included by that source file and any other file (source or header) that needs at least one of the declarations (e.g. when calling a function declared in the header file).

A special case are general header files covering project specific settings that are included by all or most files of a project.

To give some examples you should at least specify if you are using C or C++ (classes) and/or give some examples form your source file. Or show us what you have tried and where it failed.

Quote:

How do I create own header files in C language

Exactly the same as a .c file.
A header file is here to avoid typing again and again structures declarations and functions prototypes in every .c files that use them.

Imagine: you are on a big project, you have built a bunch of functions that are reused everywhere, you can type the structures declarations and functions prototypes in every .c file.

Then you need to change the structures, in this case you need to edit every single .c file that use it. It is tedious and any error will lead to weird behavior and very difficult to spot bugs.
If you use a .h header file, you have 1 place to change for the whole project.

Creating some header files isnt a good idea, because they wont have much content.

Header files are only declarations, what functions or classes will be implemented or some set of constants. They dont make sense, when implementaion of functions is missing.

You need to Learn C++[^] to use the power of the language.

As programs grow larger and larger (and include more files), it becomes increasingly tedious to have to forward declare every function you want to use that lives in a different file. Wouldn’t it be nice if you could put all your declarations in one place?