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:
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 |