Controlling Access to Class Members

You can increase the integrity of software built with C++ by controlling access to class member data and functions. Class members can be declared as having private, protected, or public access, as shown in Table 10.1.

Table 10.1   Member-Access Control

Type of Access	Meaning
private	Class members declared as private can be used only by member functions and friends (classes or functions) of the class.
protected	Class members declared as protected can be used by member functions and friends (classes or functions) of the class. Additionally, they can be used by classes derived from the class.
public	Class members declared as public can be used by any function.

Access control prevents you from using objects in ways they were not intended to be used. This protection is lost when explicit type conversions (casts) are performed.

Note   Access control is equally applicable to all names: member functions, member data, nested classes, and enumerators.

The default access to class members (members of a class type declared using the class keyword) is private; the default access to struct and union members is public. For either case, the current access level can be changed using the public, private, or protected keyword.