What is public, protected, private?

public, protected, private are access specifiers that is used to implement encapsulation of data at various level.

Private:

* Can be data or method members
* Are private to the class where they are declared
* Accessible ONLY by the member methods of the class where they are declared
* Only exception to the above rule is Friend (explanation of friends is beyond the scope of this topic
* In a C++ class, private is default for member declaration. That is, if you do not specify any access specifier (private, public, protected), the member is considered private
Public:

* Can be data or method members
* Are accessible by any function/method/application globally, so long as an instance of the class where the public members are declared is created.
* These members are accessible only thru an instance of the class where they are declared
* Generally used to define a C++ class behaviour and/or to access private data members (act as private data modifiers)

Protected

* Can be data or method members
* Act exactly as private members for all practical purposes, so long as they are referenced from within the class (and/or instances of the class)where they are declared
* Specifically used to define how certain data/method members of a class would behave in a child class (used to define their behaviour in inheritance)
* The protected members become private of a child class in case of private inheritance, public in case of public inheritance, and stay protected in case of protected inheritance.