Teach Yourself Borland C++ in 14 Days - portal

Totally Immersed: C++ Classes and Object-Oriented Programming
Anatomy of a Class
A class, like a structure, has a declaration. The class declaration is usually contained in a header
file. In simple cases, both the class declaration and the definition can be contained in a single
source file, but you typically won’t do that for real applications. Usually you create a class
source file with a filename closely matching the class name and with a .cpp extension. Because
Windows 95 and Windows NT both support long filenames, you can use filenames that
exactly match your class name if you want. The header file for the class usually has the same
name as the source file but with the extension .h. For example, if you had a class called
MyClass, you would have a source file named MYCLASS.CPP and a header named MYCLASS.H.
Class Access Levels
Classes can have three levels of access: private, public, or protected. Each of these
access levels is defined in this section.
Class access levels control how a class is utilized by users of the class. As a sole programmer,
you might be the class’s creator but also a user of the class. In team programming
environments, one programmer might be the creator of the class and other programmers are
users of the class.
NEW TERM
NOTE
Let me clarify a couple comments I made on Day 2, “Wading In
Deeper.” I said that a structure is a class in which all data members and
functions are public. In fact, in C++ this is the only thing that distinguishes
a structure from a class. A structure can have functions as well
as data members. A structure cannot use the access-modifier keywords
(private, protected, and private) because a structure can only have
public access. I also said that you probably won’t use structures very
much in your C++ programs. Because a class and a structure are nearly
the same, you will probably prefer to use classes over structures.
To understand what role levels of access play in class operation, you first need to understand
how classes will be used. In any class there is the public part of the class, which the outside
world has access to, and there is the private part of a class. The private part of a class is the
internal implementation of the class—the inner workings, so to speak.
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