Introduction to inheritance:

The capability of a class to derive properties and characteristics from another class is called Inheritance. Inheritance is one of the most important features of Object-Oriented Programming. 

Inheritance is a feature or a process in which, new classes are created from the existing classes. The new class created is called “derived class” or “child class” and the existing class is known as the “base class” or “parent class”. The derived class now is said to be inherited from the base class.

When we say derived class inherits the base class, it means, the derived class inherits all the properties of the base class, without changing the properties of base class and may add new features to its own. These new features in the derived class will not affect the base class. The derived class is the specialized class for the base class.

·         Sub Class: The class that inherits properties from another class is called Subclass or Derived Class. 

·         Super Class: The class whose properties are inherited by a subclass is called Base Class or Superclass. 

Why and when to use inheritance?

Consider a group of vehicles. You need to create classes for Bus, Car, and Truck. The methods fuelAmount(), capacity(), applyBrakes() will be the same for all three classes. If we create these classes avoiding inheritance then we have to write all of these functions in each of the three classes as shown below figure: 

Implementing inheritance in C++: For creating a sub-class that is inherited from the base class we have to follow the below syntax. 

Derived Classes: A Derived class is defined as the class derived from the base class.
Syntax: 

class  <derived_class_name> : <access-specifier> <base_class_name>
{
    //body
}

Where
class      — keyword to create a new class
derived_class_name   — name of the new class, which will inherit the base class
access-specifier  — either of private, public or protected. If neither is specified, PRIVATE is taken as default
base-class-name  — name of the base class

Modes of Inheritance: There are 3 modes of inheritance.

1.      Public Mode: If we derive a subclass from a public base class. Then the public member of the base class will become public in the derived class and protected members of the base class will become protected in the derived class.

2.      Protected Mode: If we derive a subclass from a Protected base class. Then both public members and protected members of the base class will become protected in the derived class.

3.      Private Mode: If we derive a subclass from a Private base class. Then both public members and protected members of the base class will become Private in the derived class.

Types Of Inheritance:-

1.      Single inheritance

2.      Multilevel inheritance

3.      Multiple inheritance

4.      Hierarchical inheritance

5.      Hybrid inheritance