Classes, Structures, and Unions

This section introduces C++ classes. Classes, which can contain data and functions, introduce user-defined types into a program. User-defined types in traditional programming languages are collections of data which, taken together, describe an object's attributes and state. Class types in C++ enable you to describe attributes and state, and to define behavior.

The following topics are included:

• Overview

• Class names

• Class members

• Member functions

• Static data members

• Unions

• Bit fields

• Nested class declarations

• Type names in class scope

The three class types are structure, class, and union. They are declared using the struct, class, and union keywords (see Defining Class Types). The following table shows the differences among the three class types.

For information on managed classes and structs, see Classes and Structs.

Access Control and Constraints of Structures, Classes and Unions

Structures	Classes	Unions
class key is struct	class key is class	class key is union
Default access is public	Default access is private	Default access is public
No usage constraints	No usage constraints	Use only one member at a time

See Also

Concepts

C++ Language Reference