CHAPTER 1 INTRODUCTION TO OBJECTORIENTED PROGRAMMING

1
CHAPTER 1 INTRODUCTION TO OBJECT-ORIENTED
PROGRAMMING

• ITS131
• Object-Oriented Technology

2
Objectives

• Name the basic components of object-oriented
  programming.
• Differentiate classes and objects.
• Describe the significance of inheritance in
  object-oriented programs.

3
Introduction

• A new programming paradigm
• Imperative programming (Pascal, C)
• Logic programming (Prolog)
• Functional programming (FP, Haskell)
• Object Oriented Programming (OOP) was first
  proposed in the late 1960s
• In 1990, object oriented software engineering
  became the paradigm of choice for many software
  product builder.
• Message passing is heart of OO.

4
Introduction

• Object-Oriented Language
• Java
• C
• VB
• SmallTalk
• Ada95

5
(1) OBJECT

• Object-oriented programs use objects.
• An object is a thing, both tangible (physical)
  and
• intangible (conceptual). Account, Vehicle,
• Employee, Building, etc. are examples of
  possible
• objects.
• Example 1
• For purposes of modeling a company, a CEO
• could view employees, buildings, divisions,
• documents, and benefits packages as objects.

6
(1) OBJECT

• Example 2
• An automotive engineer would see tires, doors,
• engines, top speed, and the current fuel level
  as
• objects.
• An object is comprised of data and operations
  that
• manipulate those data.

7
(2) ATTRIBUTES/ABSTRACTION

• The attributes of an object is the value of the
• object, or a set of circumstances describing
  the
• object.
• Example 1
• The attributes of an electric light bulb would
  be
• "on" or "off" .
• Example 2
• The attributes of a clock object would be the
  time .

8
(3) OPERATIONS

• An object encapsulates data ( represented as a
• collection of attributes).
• Operations is the algorithm that process the
  data.
• Each of the operation of the object represent
  the
• behavior of the object.

9
(4) CLASS

• Inside a program we write instructions to create
• objects. For the computers to be able to create
  an
• object, we must provide a definition called a
  class.
• A class is a kind of template that the computer
• uses to create objects, so a class must be
  defined
• before you can create an object of the class.
• In other way, a class is a generalized
  description
• that describes a collection of similar
  objects.

10
(4) CLASS

• An object is called an instance of a class.
• An object is an instance of exactly one class.
• An instance of a class belongs to the class.
• Example
• Class Customer
• Objects Jack and Jill
• Jack and Jill are the instances of Customer
• Two Customer objects with the names of Jack and
• Jill.

11
(4) CLASS

• Representation of Object Oriented Class

ATTRIBUTES
CLASS NAME
CLASS NAME Furniture

ATTRIBUTES -color -price -weight -dimension
OPERATIONS
OPERATIONS -buy -sell
12
(5) MESSAGES

• To instruct a class or an object to perform a
  task,
• we send a message to it.
• You can send a message only to the classes and
• objects that understand the message you sent
  to
• them.

13
(5) Messages
Class name FEES PAYMENT
Class name STUDENT
Attributes -name -subjects taken -payment
Attributes -name -IC -course -subjects
Operations -Total payment
Operations Register subject
MESSAGE
Message passing between two objects
14
(6) METHODS

• A class or an object must possess a matching
• method to be able to handle the received
  message.
• A method defined for a class is called a class
• method, and a method defined for an object is
• called an instance method.

15
(7) INHERITANCE

• In object-oriented programming, we use a
• mechanism called inheritance to design two or
• more entities that are different but share
  many
• common features.

16
(7) INHERITANCE

• First, we define a class that contains the
• common features of the entities.
• Then we define classes as an extension of the
• common class inheriting everything from the
• common class.

17
(4) INHERITANCE

• We call the common class the superclass and all
• classes that inherit from it subclasses.
• We also call the superclass an ancestor and the
• subclass a descendant.

18
(4) INHERITANCE

Class name FURNITURE Attributes
SUPERCLASS
OPERATIONS

SUBCLASS
Class name TABLE
Class name CHAIR
Class name DESK
Attributes
Attributes
Attributes
OPERATIONS
OPERATIONS
OPERATIONS