# Header files
A header file is a C file that should contain the following:

* **external function declarations**
* **macro definitions (preprocessor #defines)**
* structure, union, and enumeration declarations
* typedef declarations
* global variable declarations


Header files are generally used to save changing a lot of separate function declarations when you change something.

See also https://c-faq.com/cpp/hfiles.html
 

# Include gaurds
To protect against multiple and circular includes, include this in your header file:
```c
#ifndef MYHEADER_H
#define MYHEADER_H

// ... header content ...

#endif
```