Every Object Has A Type

Each object is an instance of a class, where 'class' is synonymous with 'type'. Object oriented terms use the word class to refer to the properties, events, and methods that uniquely define a type of object.

A class contains the information that is needed to create an object of that class.

The form and controls you use to build a program are actually instances of their respective classes. The most important distinguishing characteristic of a class is "what messages can you send to it?"

Objects Have Life Cycles

To be used, objects must be created. At some point, when they are not needed any more, they should be destroyed because they use resources. When an object is destroyed, the memory that was being used by that object is freed and is then available for reuse.

In this chapter, you have been introduced to event driven model and object-oriented programming. Now you should understand what is meant by the terms object, instance, class, property, event, and methods.