You can include other files using the include statement

How to Include

The preprocessor allows you to include the contents of one file in another. This is performed using the #include statement.

• OPTION 1: If the name of the file to be included is enclosed in angle brackets < >, the compiler will search a standard list of directories for the file you wish to include; you can add entries to this list with the compiler flag -I.
• OPTION 2: If the name of the file is in quotes " ", it will search the current directory for the files in addition to the other directories.

#include <math.h>
#include <stdio.h>
#include "MyHeader.H"

When to include header file of a class

The following is a non-exhaustive list of times when you will need to include the header file for a class:

• when you create an instance of the class
• when you call a member function on an instance of the class
• when you access a public instance variable on an instance of the class
• when you access a static function or member of the class
• when you define methods for the class (i.e. Foo.C must include Foo.H)
• when you declare a member instance in the class declaration
• when the class you're declaring is a subclass of the class (i.e. SubClass.H must include SuperClass.H)