Unformatted text preview: imitive element of a program written in an OOP language. Each
object consists of a set < procedures (known as methods) and some data. It stores
the data in variables and responds to messages received from other objects by
executing the procedures (methods). A method is a collection of operations that
specifics the reaction of the object when it receives a message that corresponds to
A program written in a pure OOP language is a collection of objects that
communicate with each other. Virtually everything, from items as simple as the
integer constant 8 to a complex file-handling system, are objects. As objects, they
are treated uniformly. They all have local memory, inherent processing ability, the
capability to communicate with other objects, and the ability to inherit
characteristics from ancestors.
Each object can be viewed as an abstract data type because it is an autonomous
entity with its private data and methods. Note that an object contains both
functions (procedures/methods) and data that describe the characteristics of the
object. In other words, an object encapsulates both data and functions.
A method of an object defines the set of operations that the object will execute
when a message corresponding to the method is received by the object. In a sense,
methods are like function definitions, complete with parameters and the capability
of returning values. The binding of a message to a method is dynamic. The entire
collection of methods of an object is called the message protocol, or message
interface, of the object. Figure 12.13 illustrates the object model used in OOP. Message
The mechanism to support communication between objects is through messages.
That is, all computing in a program written in an OOP language is done by
sending a message to an object to invoke one of its methods. A reply to a message
is an object, which returns the requested information, or simply notifies the sender
that the requested processing has been completed.
There is a fundamental difference between a message sent to...
View Full Document
This document was uploaded on 04/07/2014.
- Spring '14