Header file

From DmWiki

A header file or 'dot-h' file are one of two primary files used in compiling C/C++ code. A header file contains 'prototype declarations' (formatted descriptors) of functions which will later be implimented in compiled code. They also sometimes contain macros, preprocessor definitions, class definitions, or anything that may need to be shared among multiple source code files.

For example, if you create a function

int Add( int n1, int n2 );

and want to access it in several of your source code files you might put this definition in a file called 'functions.h'.

Within each of your C/C++ files, the addition of

#include "functions.h"

tells the preprocessor to look in that file for functions which will be later defined and are therefor allowable.