Object-oriented programming (OOP) is a computer programming framework. The fundamental principle of object-oriented programming is that a computer program is composed of a collection of individual units, or objects which can function like sub-programs. Object Oriented Programming solve three main software engineering goals: Re-usebility, flexibility and extensibility. To make the overall computation happen, each object is capable of receiving messages, processing data, and sending messages to other objects. OOP has the following key concepts and components:

• Objects – units of data and functionality together within a running computer program; objects are the basis of modularity and structure in an object-oriented computer program.
• Abstraction - The ability for a program to ignore some aspects of the information that it is manipulating, i.e. the ability to focus on the essential.
• Encapsulation - Also called information hiding: Ensures that objects cannot change the internal state of other objects in unexpected ways; only the object's own internal methods are allowed to access its state. Each type of object exposes an interface to other objects that specifies how other objects may interact with it.
• Polymorphism - References to and collections of objects may refer to objects of different types, and invoking an operation on a reference will produce behavior depending on the actual type of the referent.
• Inheritance - Organizes and facilitates polymorphism and encapsulation by allowing the creation of decedent objects from existing objects. This is typically done by grouping objects into classes, and defining classes as extensions of existing classes, thus and grouping classes into trees or lattices reflecting behavioral commonality.

Object-based programming has become especially popular in scripting programming languages, with abstraction, encapsulation, reusability, and ease of use being the most commonly cited reasons. Python and Ruby are relatively recent languages that were built from the ground up with OOP in mind, while the popular Perl scripting language has been slowly adding new object oriented features since version 5. The ability of objects to represent "real world" entities is one reason for the popularity of JavaScript (ECMAScript), which is argued to be well suited to representing the Document Object Model of HTML and XML documents on the Internet.

OOP: Object Oriented Programming

Related Terms: HTML, XML, Perl, Java Script

Reference Links: http://www.zib.de/Visual/people/mueller/Course/Tutorial/tutorial.html: Object Oriented Programming Tutorial