0.3 Xna0104-what is oop and why should you care?  (Page 2/7)

For example, an OO program that deals with banking transactions should be recognizable on the basis of the objects that it uses, such as deposit objects,withdrawal objects, account objects, etc.

An anecdotal description

If you have ever assembled a playscape in your back yard, this should sound familiar to you.

When you opened the large boxes containing the playscape, hundreds of objects spilled onto the ground. Those objects may have consisted of braces, chains,swing seats, slides, screws, nuts, bolts, washers, climbing ropes, ladder rungs, and other assorted objects.

Atomic and non-atomic objects

I will refer to (most of) the kinds of object that I have described in the above list as atomic objects. What I mean by that is that they can't be easilysubdivided into smaller objects without destroying their functionality.

If you were lucky, some of the objects in the box may not have been atomic objects. Instead they may have been pre-assembled arrangements of atomic objectssuch as an assembly of seats and braces representing a object on which two children can swing together.

Your job - assemble the objects

Your job was to assemble those hundreds of atomic and non-atomic objects into a final object which you proudly referred to as "The Playscape."

Objects working together

It has been said that a successful object-oriented program consists of a bunch of cooperating software objects working together to achieve a specifiedbehavior.

The overall behavior of the program is the combination of behaviors of the individual objects. For example, some objects may acquire input data, otherobjects may compute and produce output data, while other objects may display the output data.

It could also be said that a playscape consists of a bunch of hardware objects working together to achieve a specified behavior. The overall behaviorof the playscape is the combination of behaviors of the individual objects. For example, the behavior of some of the braces is to stand strong and not bend,while the behavior of a swing chain is to be flexible and move in a prescribed way.

Creating a model

One of the tasks often faced by an object-oriented programmer is to assemble software objects into a model that represents something that exists in the real world. As a very visual example, you might be asked to create an advertising webpage showing an animated software model of the playscape that you assembled in your back yard. With the playscape, you were simply required to assemble theexisting objects. However, in the object-oriented programming world, you must do more than just assemble objects.

Objects must be designed and manufactured

Getting back to the playscape, each of the objects for the playscape was manufactured before being shipped to you. Even before that, each object wasdesigned by someone and a set of manufacturing drawings was probably created so that the object could be mass produced.

A class is analogous to manufacturing drawings

In OOP, there is a direct analogy to the manufacturing drawings of the hardware world. We call it a class . A class documents the specifications for the construction of a particular type of software object. Forexample, there is probably a set of classes that describe the specifications for each of the button objects and menu objects at the top of the browser in whichyou are currently viewing this module.