Object-oriented programming (OOP) - An object is actually a discrete bundle of functions and procedures, all relating to a particular real-world concept such as a bank account holder or football player in a computer game. Other pieces of software can access the object only by calling its functions and procedures that have been allowed to be called by outsiders. Isolating objects in this way makes their software easy to manage and keep track of. For example, the football player's functions might include one to reveal the player's current position on the field, and another to instruct the player to kick the ball. The account holder's functions might include one to reveal the current balance or to draw out a sum.
Object-oriented programming has roots that can be traced to the 1960s. As hardware and software became increasingly complex, quality was often compromised. Researchers studied ways to maintain software quality and developed object-oriented programming in part to address common problems by strongly emphasizing discrete, reusable units of programming logic. The methodology focuses on data rather than processes, with programs composed of self-sufficient modules (objects) each containing all the information needed to manipulate its own data structure. This is in contrast to the existing modular programming which had been dominant for many years that focused on the function of a module, rather than specifically the data, but equally provided for code reuse, and self-sufficient reusable units of programming logic, enabling collaboration through the use of linked modules (subroutines). This more conventional approach, which still persists, tends to consider data and behavior separately.
An object-oriented program may thus be viewed as a collection of interacting objects, as opposed to the conventional model, in which a program is seen as a list of tasks (subroutines) to perform. In OOP, each object is capable of receiving messages, processing data, and sending messages to other objects and can be viewed as an independent 'machine' with a distinct role or responsibility. The actions (or "operators") on these objects are closely associated with the object. For example, the data structures tend to 'carry their own operators around with them' (or at least "inherit" them from a similar object or class).
In recent years, object-oriented programming has become especially popular in scripting programming languages. Python, Ruby and Groovy are scripting languages built on OOP principles, while Perl and PHP have been adding object oriented features since Perl 5 and PHP 4, and ColdFusion since version 6. The Document Object Model of HTML, XHTML, and XML documents on the Internet have bindings to the popular JavaScript/ECMAScript language. JavaScript is perhaps the best known prototype-based programming language, which employs cloning from prototypes rather than inheriting from a class. Another scripting language which takes this approach is Lua. Earlier versions of ActionScript (a partial superset of the ECMA-262 R3, otherwise known as ECMAScript) also used a prototype based object model. Later versions of ActionScript incorporate a combination of classification and prototype based object models based largely on the currently incomplete ECMA-262 R4 specification, which has its roots in an early JavaScript 2 Proposal. Microsoft's JScript.NET also includes a mash-up of object models based on the same proposal, and is also a superset of the ECMA-262 R3 specification.