What is inheritance in C++?

Inheritance is one of the pillars in Object oriented programming. There are many types of inheritance. Single inheritance is the one which involves derived class inherited from a single base class. Multiple inheritance is when a derived class inherits from two or more base classes. Multilevel inheritance occurs when a class is inherited from a derived class, which itself is derived from a base class. Hierarchical inheritance occurs when two or more classes are derived from the same base class. Hybrid inheritance is the combination of the types mentioned. Usually, this is not much in use.

Single Inheritance: The derived class 'Truck' inherits from the single base class 'Vehicle'. Multiple Inheritance: Derived class 'MultimediaPlayer' derives from two base classes 'AudioPlayer' and 'VideoPlayer' Multilevel Inheritance: Base class 'Animal', derived class 'Mammal' (inherits from 'Animal'), and further derived class 'Human' (inherits from 'Mammal'). Hierarchical Inheritance: Base class 'Shape' and two derived classes 'Circle' and 'Square', both inheriting from the common base class 'Shape'. Hybrid Inheritance: class 'TeamLead' inherits from both 'Manager' and 'ProjectLeader', combining elements of single, multiple, and multilevel inheritance.

We can understand easily like, BASE CLASS -> DERIVED CLASS. For example, - Single: Single base class, single derived class. Like Vehicle->Car - Multiple: Multiple base class, single derived class. Like, Father->Child, Mother->Child - Multilevel: Multi-levels of base classes, where the derived class will be the base class of another class. Like, Vehicle->Flying Vehicle->Helicopter. - Hierarchical: Single Base class, multiple derived class. Like, Company->HR, Company->Sales. Company->Policy - Hybrid: Combination of One or more Base classes & One or more derived classes, Like, Student->Exam, Student->Project, Exam->Result, Project->Result Kindly note, here -> (arrow) signs is not standard, but we can use it for easy understanding.

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. (Credit:Gfg)

The syntax is very simple, It's like class DC : AS BC { // derived class members }; here, class is the keyword, DC = Derived Class Name (You need to write your derived class name here). BC = Base Class Name (You need to write your base class name here). AS = Access Specifier which was officially known as Access Modifiers, Access Specifier is the new term. Access Specifier can be either public, protected, or private. Here, "public" means their members can be accessible by anyone either derived class or their instances. "protected" means their members can be accessible by derived classes or sub-classes. "private" means their members cannot be accessible anywhere outside of class, it's for internal purposes only.

An access specifier controls how parts of a class (like variables and functions) can be seen and used from outside the class. There are three types: Public: Accessible from anywhere, both inside and outside the class. Protected: Accessible within the class and its subclasses (derived classes). Private: Accessible only within the class; not visible to derived classes or external code. Syntax of Inheritance : class derived_class : access_specifier base_class { // derived class members } Example: class circle : public shape{ // derived class members }

The benefits of inheritance in C++ are: Code Reusibility: Inheritance lets us reuse code from one class in another without having to write it all over again. Extensibility: We can add new things or change existing ones in a class that inherits from another. It's like adding extra features to a base class. Polymorphism: With inheritance, we can use the same name for different things in different classes, as long as they work in a similar way. It's like having different tools with the same name but doing different jobs.

Interface inheritance is a mechanism that allows a class to inherit method declarations from one or more interfaces. An interface in programming defines a contract of methods that a class implementing the interface must provide. Polymorphism is the ability of objects to take on multiple forms. In the context of interface inheritance, polymorphism is often achieved through a concept known as interface polymorphism or runtime polymorphism.

Inheritance is indeed a very easy concept in C++, but make sure you always use RAII (Resource Acquisition is Initialization) I think it's required because, when the exception is thrown and the stack is unwound, the local variables or relevant class member values are destroyed which ensures that our resource is cleaned up and doesn't leak.