Inheritance in C++ Programming | C++ Programming

Inheritance in C++ Programming 

Introduction Inheritance (or derivation) is the process of creating new classes, called derived classes, from existing classes, called base classes. The derived class inherits all the properties from the base class and can add its own properties as well. The inherited properties may be hidden (if private in the base class) or visible (if public or protected in the base class) in the derived class.

Inheritance uses the concept of code re-usability. 

Once a base class is written and debugged, we can reuse the properties of the base class in other classes by using the concept of inheritance. Reusing existing code saves time and money and increases program’s reliability. An important result of re usability is the ease of distributing classes. A programmer can use a class created by another person or company, and, without modifying it, derive other classes from it that are suited to particular situations.

Types of Inheritance 

A class can inherit properties from one or more classes and from one or more levels. On the basis of this concept, there are five types of inheritance.
1. Single inheritance
2. Multiple Inheritance
3. Hierarchical Inheritance
4. Multilevel Inheritance
5. Hybrid Inheritance

  Single Inheritance 

In single inheritance, a class is derived from only one base class. The example and figure below show this inheritance.
Example

class A
{
 members of A
};
class B  :  public A
{
 members of B
};

Multiple Inheritance 

In this inheritance, a class is derived from more than one base class. The example and figure below show this inheritance.

Implementation Skeleton: 

class A
{  members of A };
class B
{  members of B };
class C  :
public A,
public B 
{  members of C };

Hierarchical Inheritance 

In this type, two or more classes inherit the properties of one base class. The example and figure below show this inheritance.

Implementation Skeleton:

class A
{  members of A };
 class B 
{  members of B };
class C  :  public A,  public B 
{  members of C };

Multilevel Inheritance

 The mechanism of deriving a class from another derived class is known as multilevel inheritance. The process can be extended to an arbitrary number of levels. The example and figure below show this inheritance.

Implementation Skeleton:

class A 
{  members of A };
class B : public A 
{  members of B };
class C  :  public B 
{  members of C };

Hybrid Inheritance 

This type of inheritance includes more than one type of inheritance mentioned previously. The example and figure below show this inheritance.
Example
class A
{
 members of A
};
class B : public A
{
 members of B
};
class C  :  public A 
{
 members of C
};
class D : public B, public C
{
 members of D
};