Properties of Object Oriented Systems. Dot Net Interview Questions

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Note:- Difference between abstraction and encapsulation is one of the favorite interview question and quiet confusing as both the terminology look alike.Best is if you can brainstorm with your friends or do a little reading.

Following are characteristic’s of Object Oriented System’s :-

Abstraction

It allows complex real world to be represented in simplified manner.Example color is abstracted to RGB.By just making the combination of these three colors we can achieve any color in world.It’s a model of real world or concept.

Encapsulation

The process of hiding all the internal details of an object from the outside world. Communication using messagesWhen application wants to achieve certain task it can only be done using combination of objects.

A single object can not do all the task.Example if we want to make order processingform. We will use Customer object , Order object , Product object and Payment object toachieve this functionality.In short these objects should communicate with each other.Thisis achieved when objects send messages to each other.

Object lifetime

All objects have life time.Objects are created , initialized , necessary functionalities are done and later the object is destroyed.Every object have there own state and identity ,which differ from instance to instance.

Class hierarchies (Inheritance and aggregation)

In object oriented world objects have relation and hierarchies in between them.There are basically three kind of relationship in Object Oriented world :-

Association
This is the simplest relationship between objects.Example every customer has sales.So Customer object and sales object have a association relation between them.

Aggregation

This is also called as composition model.Example in order to make a “Accounts” class it has use other objects example “Voucher”,”Journal” and “Cash” objects.So accounts class is aggregation of these three objects.

Inheritance

Hierarchy is used to define more specialized classes based on a preexisting generalized class.Example we have VEHICLE class and we can inherit this class make more specialized class like CAR, which will add new attributes and use some existing qualities of the parent class.Its shows more of a parent-child relationship .This kind of hierarchy is called inheritance.

Polymorphism

When inheritance is used to extend a generalized class to a more specialized class,it includes behavior of the top clas(Generalized class).The inheriting class often implement a behavior that can be somewhat different than the generalized class, but the name of the behavior can be same.It is important that a given instance of an object use the correct behavior, and the property of polymorphism allows this to happen automatically.