Classes: The Basics - Illustrated C# 2005 - page 44

Overview of Classes
In the previous chapter, you saw that C# provides six user-defined types. The most important
of these, and the one I will cover first, is the class . Since the topic of classes in C# is a large one,
its discussion will be spread over the next several chapters.

A Class Is an Active Data Structure
Before the days of object-oriented analysis and design, programmers thought of a program as
just a sequence of instructions. The focus at that time was on structuring and optimizing those
instructions. With the advent of the object-oriented paradigm, the focus changed from opti-
mizing instructions to organizing a program's data and functions into encapsulated sets of
logically related data items and functions, called classes.
A class is a data structure that can store data and execute code. It contains the following:

￿ Data members , which store data associated with the class or an instance of the class.

Data members generally model the attributes of the real-world object the class
represents.

￿ Function members , which execute code. Function members generally model the func-

tions and actions of the real-world object that the class represents.

A C# class can have any number of data and function members. The members can be any
combination of nine possible member types. These member types are shown in Table 4-1. The
ones I will cover in this chapter— fields and methods —are checked in the table.

Table 4-1. Types of Class Members

Data Members Store Data Function Members Execute Code

✓ Fields ✓ Methods ❏ Operators

❏ Constants ❏ Properties ❏ Indexers

❏ Constructors ❏ Events

❏ Finalizers

■ Note Classes are encapsulated sets of logically related data items and functions that generally represent
objects in the real world or a conceptual world.