C++ Inheritance

One of the most important concepts in object-oriented programming is that of inheritance. Inheritance is a mechanism of reusing and extending existing classes without modifying them, thus producing hierarchical relationships between them and provides an opportunity to reuse the code functionality and fast implementation time.

When creating a class, instead of writing completely new data members and member functions, programmer can designate that the new class should inherit the members of an existing class. This existing class is called the base class, and the new class is referred to as the derived class.

Forms of Inheritance

• Single Inheritance – If a class is derived from a single base class, it is called as single inheritance.
• Multiple Inheritance – If a class is derived from more than one base class, it is known as multiple inheritance.
• Multilevel Inheritance – The classes can also be derived from the classes that are already derived. This type of inheritance is called multilevel inheritance.
• Hierarchical Inheritance – If a number of classes are derived from a single base class, it is called as hierarchical inheritance.
• Hybrid Inheritance – This is a Mixture of two or More Inheritance and in this Inheritance a Code May Contains two or Three types of inheritance in Single Code.

Visibility Mode

It is the keyword that controls the visibility and availability of inherited base class members in the derived class. It can be either private or protected or public.

• Private Inheritance – When deriving from a private base class, public and protected members of the base class become private members of the derived class.
• Public Inheritance – When deriving a class from a public base class, public members of the base class become public members of the derived class and protected members of the base class become protected members of the derived class. A base class’s private members are never accessible directly from a derived class, but can be accessed through calls to the public and protected members of the base class.
• Protected Inheritance – When deriving from a protected base class, public and protected members of the base class become protected members of the derived class.

Base class visibility	Derived class visibility
	Public derivation	Private derivation	Protected derivation
Private	Not inherited	Not inherited	Not inherited
Protected	Protected	Private	Protected
Public	Public	Private	Protected