1  
 2  This directory is intended for project header files.
 3  
 4  A header file is a file containing C declarations and macro definitions
 5  to be shared between several project source files. You request the use of a
 6  header file in your project source file (C, C++, etc) located in `src` folder
 7  by including it, with the C preprocessing directive `#include'.
 8  
 9  ```src/main.c
10  
11  #include "header.h"
12  
13  int main (void)
14  {
15   ...
16  }
17  ```
18  
19  Including a header file produces the same results as copying the header file
20  into each source file that needs it. Such copying would be time-consuming
21  and error-prone. With a header file, the related declarations appear
22  in only one place. If they need to be changed, they can be changed in one
23  place, and programs that include the header file will automatically use the
24  new version when next recompiled. The header file eliminates the labor of
25  finding and changing all the copies as well as the risk that a failure to
26  find one copy will result in inconsistencies within a program.
27  
28  In C, the convention is to give header files names that end with `.h'.
29  
30  Read more about using header files in official GCC documentation:
31  
32  * Include Syntax
33  * Include Operation
34  * Once-Only Headers
35  * Computed Includes
36  
37  https://gcc.gnu.org/onlinedocs/cpp/Header-Files.html