C plus plus study note (one)

What is an object ?

Object = Entity ;

Object may be

• -- visible or
• -- invisible

Object is variable in programming languages.

Objects = Attributes + Services

What is Object-oriented

A way to organize

• Designs
• Implementations

Objects send messages

Messages are

• -Composed by the sender
• -Interpreted by the receiver
• -Implemented by methods

Messages

• May cause receiver to changer state
• May return results

Object vs. Class

OOP characteristics

• A program is a bunch of objects telling each other what to do by sending messages.
• Each object has its own memory made up of other objects
• Every object has a type.
• All objects of a particular type can receive the same messages.

The Hidden Implementation

Inner part of an object, data members to present its state, and the actions it takes when messages is rcvd is hidden.

Class creators vs. Client programmers

-keep client programmers' hands off portions they should not touch

-Allow the class creators to change the internal working of the class without worrying about how it will affect the client programmers.

Encapsulation

Bundle data and methods dealing with these data together in an object.

Hide the details of the data and the action.

Restrict only access to the publicized methods.