1

OBJECT ORIENTED PROGRAMMING OVERVIEWChapter 1

2

Introduction Aims:• to establish understanding of basic

concepts of Object Oriented Programming (OOP)

What will be covered:• Procedural Programming vs OOP• History of OOP• Object Oriented Application• basic concept of OOP

3

Introduction There are two most widely used

programming language styles:

1. Procedural Programming

2. Object Oriented Programming

4

Procedural Vs Object Oriented Programming

• Procedural programming• also known as structural programming

languages • This type of style allows programmers to

write program according to a set of steps for solving problems, usually in a top down manner and in chronological order.

• It relies on functional decomposition which means the system is broken down into components/ functions/ procedures.

• The programming relies heavily on the 3 basic structures: sequence, selection and iteration.

• using traditional programming languages e.g. C, Fortran, Cobol etc.

5

Object-oriented programming The world around us are made up of

objects e.g. people, cars, trees, buildings etc

This is used to model a software system as a set of objects interacted with each other.

The Objects represent the system components

Each OO program file must contain at least one class

Some of the programming language used are Java, C++, C#, VB.NET etc.

Procedural Vs Object Oriented Programming

6

Object-Oriented Programming is VERY different from procedural programming.   Instead of think of "steps/processes" to

solving a problem, we need to think about and identify the objects involved in the

problem and how they'll interact. Each object is responsible for its own activities and data.

OO developer however must still follow the step of understanding the problem

andplanning the application

Procedural Vs Object Oriented Programming

7

Data

Application file:VariablesMethods

InputOutput

Data

Application file:Input

OutputObject creation

Class file: variablesmethods

Class file: variablesmethods

Class file: variablesmethods

PROCEDURAL APPLICATION

OBJECT ORIENTED APPLICATION

Procedural Vs Object Oriented Programming

8

The previous diagrams shows that In procedural programming,

• all input, output, variables and methods are put in a single file.

• This is quite large and difficult to maintain

In Object Oriented Programming, • most variables and methods are organized

within separate classes that define different kind of objects.

• A separate, smaller application file handles input and output and creates the needed objects.

• OO approach produces more modular and organized application

Procedural Vs Object Oriented Programming

9

Architecture - JavaOO program file

e.g. calculateSalary.java

Class/ese.g. calculateSalary

Method/se.g. (main)

Statementse.g. System.out.println(“Please enter hours worked”)

10

Object Oriented Approach Object oriented approach intended to

produce systems which are composite, modular constructions, build using abstraction, and organized around the data.

Suitable to solve large and evolving software system.

Most research claimed that OO IS is much easier to maintain compared to the traditional IS.

11

History of OOP Object programming was reported to exists

in Simula 67 back in 1960s Simula 67 is developed at the Norwegian

Computing Center in Oslo, by Ole-Johan Dahl and Kristen Nygaard.

Simula 67 is used to program Simulation Influenced from Simula 67, later, the theory

of OOP is introduced by smallTalk (Xerox PARC) which further designed it to include the pervasive use of objects and messages as the basis for computation.

Mid 1980s, OOP dominant the programming methodology through C++ (an extension of C Language)

More recently, a number of OOP languages exists such as Visual Basic .NET, C#

12

Object Oriented Programming Why is Object Oriented introduced?

Object Oriented Programming is introduced because of the limitation of the procedural programming which are:

• programs written in procedural language become complex very quickly (1000s lines of code) if very large system is developed

• difficult to test and maintain• often re-implement code unnecessarily (a

large system is normally programmed by more than 1 developer

13

Object-Oriented programming uses 3 main concepts: Inheritance – copying the

attributes and methods from the base/parent classes

Encapsulation – data hiding (hiding the attributes from the outside world)

Polymorphism – using methods of the same name for a variety of purposes (overriding or overloading)

Object Oriented Programming

14

Object Oriented Terms and ConceptsAn object simply represents any object that you may think of in the "real world".

Tangible (like real objects that you can touch): e.g., a House, a Car, a Person, etc...

Non tangible objects (sometimes harder to identify):

e.g., a BankAccount, Insurance, a Loan, a Vacation, etc...

15

Objects are made up of two "things": state (a.k.a.

attributes/fields/properties + value) A given set of data which describes the

object e.g., colour, size, amount, name,

phoneNumber, etc...

behaviour (a.k.a. methods or functions) A set of operation that the object can

perform e.g., walk, run, drive, sell, buy, transfer,

computeTotal, open, close, etc...

Object Oriented Terms and Concepts

16

withdraw, deposit, transfer, get balance

owner, balance, accountnumberBankAccount

make purchase, list items bought, return

item

name, address,purchase history

Customer

get the address, change phone number

name, age, gender, phone numberPerson

BehaviourStateObject

Example of Object, state, behaviour

Object Oriented Terms and Concepts

17

• An object is a specific item in the class, often referred to an instance/example of a class.

• A class is simply a template/mould/blueprint for constructing objects of a specific type.

• Before you can use an object in your program, you MUST define the class.   In fact, ALL objects MUST belong to a class of some kind.

Object Oriented Terms and Concepts

18

Instances of fruit

An instance of the Fruit class refers to a specific fruit.These are all objects

Class : Fruit

Object Oriented Terms and Concepts

19

Construction of OO Programming So how do we actually write an

Object-Oriented program ?

• Identify  the Objects (i.e., Classes) that represent our problem which is to be solved (or simulated)

• identify the object characteristics (i.e., state and behaviour)

• Identify the inter-relationships between the Objects (i.e., how they interact).

20

ExampleScheduling application Involves objects such as:

Students Course Schedule

Objects attributes Student – ID, name, gender, dob Course – dept, number, descr, credit hrs Schedule – semester, studentID, a number

of courses Object behaviour

Schedule – assign studentID and course20

21

Exercise Identify 3 objects that might

belongs to each of the following classes: automobile animal bankAccount footballPlayer mobilePhone

21