An object oriented system revolves around a Class and objects. A class is used to describe characteristics of any entity of the real world. An object is a pattern of the class. An actual object created at runtime is called as an instance. A class, apart from characteristics has some functions to perform called as methods. For.e.g A class named “Food” has attributes like ‘price’, ‘quantity’. “Food” class has methods like Serve_food(), bill_food().

Objects in Object Oriented Systems interact through messages.

• Inheritance:- The main class or the root class is called as a Base Class. Any class which is expected to have ALL PROPERTIES of the base class along with its own is called as a DERIVED class. The process of deriving such a class is Derived class. For the “Food” class, a Derived class can be “Class Chinesefood”.
• Abstraction:- Abstraction is creating models or classes of some broad concept. Abstraction can be achieved through Inheritance or even Composition.
• Encapsulation:- Encapsulation is a collection of functions of a class and object. The “Food” class is an encapsulated form. It is achieved by specifying which class can use which members (PRIVATE, public, protected) of an object.
• Polymorphism:- Polymorphism means existing in different FORMS. Inheritance is an EXAMPLE of Polymorphism. A base class exists in different forms as derived classes. Operator overloading is an example of Polymorphism in which an operator can be applied in different situations.

An object oriented system revolves around a Class and objects. A class is used to describe characteristics of any entity of the real world. An object is a pattern of the class. An actual object created at runtime is called as an instance. A class, apart from characteristics has some functions to perform called as methods. For.e.g A class named “Food” has attributes like ‘price’, ‘quantity’. “Food” class has methods like Serve_food(), bill_food().

Objects in Object Oriented Systems interact through messages.