This article introduces readers to OOPS (object-oriented programming system) and focus on its characteristics in little details.
According to Wikipedia, Object-oriented programming (OOP) is a programming paradigm that uses "objects" and their interactions to design applications and computer programs. Programming techniques may include features such as abstraction, encapsulation, inheritance, and polymorphism. In this article I will try to descibe each one of them.
In order to understand this article, you should know basics concepts of an object, class. Lets see what are they.
Basically an object is anything that is identifiable as an single material item. You can see around and find many objects like Camera, Monitor, Laptop etc. In OOP perspective, an object is nothing but an instance of a class that contains real values instead of variables
A class is a template definition of the methods and variables for a particular kind of object. In other words, class is the blue print from which an individual objects are created.
Now lets see basic features of Object Oriented Programming one by one.
Abstraction is a process of identifying the relevant qualities and behvaiors an object should possess. Lets take an example to understand abstraction. A Laptop consists of many things such as processor, motherboard, RAM, keyboard, LCD screen, wireless antena, web camera, usb ports, battery, speakers etc. To use it, you don't need to know how internally LCD screens, keyboard, web camera, battery, wireless antena, speakers works. You just need to know how to operate the laptop by switching it on. The intrinsic details are invisible. Think about if you would have to call to the engineer who knows all internal details of the laptop before operating it. This would have highly expensive as well as not easy to use everywhere by everyone. So here the Laptop is an object that is designed to hide its complexity.
Think If you need to write a piece of software to track the students details of a school, you may probably need to create Students objects. People comes in all different backgrounds, educational qualifications, locations, hobbies, ages and have multiple religion, language but in terms of application, an student is just a name, age, class and roll number, while the other qualities are not relevant to the application. Determining what other qualities (background, qualifications, location, hobbies etc) are in terms of this application is abstraction.
In object-oriented software, complexity is managed by using abstraction. Abstraction means showing only those details to the user that he needs and eliminating/hiding irrelevant and complex details. A well thought-out abstraction is usually simple, and easy to use in the perspective of the user, the person who is using your object.
Encapsulation is a method for protecting data from unwanted access or alteration by packaging it in an object where it is only accessible through the object's interface. Encapsulation are often referred to as information hiding. But both are different. In fact information hiding is actually the result of Encapsulation. Encapsulation makes it possible to separate an object's implementation from its original behavior - to restrict access of its internal data. This restriction facilitate certain details of an object;s behavior to be hidden. This allows to protect an object's internal state from corruption by its user.
It is the mechanism by which Abstraction is implemented. In other words you can say that Abstraction is the result of the Encapsulation. For example, the Laptop is an object that encapsulates many technologies/hardware that might not be understood clearly by most people who use it.
Inheritance is the ability to define a new class or object that inherits the behavior and its functionality of an existing class. The new class or object is called a child or subclass or derived class while the original class is called parent or base class. For example, in a software company Software Engineers, Sr. Software Engineers, Module Lead, Technical Lead, Project Lead, Project Manager, Program Manager, Directors all are the employees of the company but their work, perks, roles, responsibilities differs. So in OOP, the Employee base class would provide the common behaviors of all types/level of employee and also some behaviors properties that all employee must have for that company. The particular sub class or child class of the employee would implement behaviors specific to that level of the employee. So by above example you can notice that the main concept behind inheritance are extensibility and code reuse (in this case you are extending the Employee class and using its code into sub class or derived class).
As name suggests, Polymorphism means an ability to assume different forms at different places. In OOP, it is a language's ability to handle objects differently based on their run time type and use. Polymorphism is briefly described as "one interface, many implementations".Polymorphism is a characteristic of being able to assign a different meaning or usage to something in different contexts - specifically, to allow an entity such as a variable, a function, or an object to have more than one form.
There are two types of polymorphism.
- Compile time polymorphism - It is achieved by overloading functions and operators
- Run time polymorphism - It is achieved by overriding virtual functions
Lets say you have a class that have many Load methods having different parameters, this is called Compile time polymorphism. Lets take another example where you have a virtual method in the base class called Load with one parameter and you have redefined its functionality in your sub class/ child class by overriding base class Load method, this is called Run time polymorphism.
In this small article, I have tried to explain basic features of OOPS in little details. OOPS in itself is a very vast subject and explaining each and every features is near to impossible for me. If you have any comments of suggestions, please respond to this article.
Take care and thank you very much for reading.