Introduction to

Object Oriented Concepts

بسم هللا الرحمن الرحيم

Prepared By:

Eng.\ Tarig Ahmed Khalid, M.Sc., PMP, CEC, CBAP

General Features of Programs

Input Output Processing

Data Information a. Logic

+

b. Syntax

Data / Information

Primitive Data Type Abstract Data Type

Numeric Character

Integral Real

Classes

1. Classical Programming.

2. Structured Programming.

3. Object Oriented Programming.

Evolution of Programming Techniques

Input x,y,z

…..

……..

If x>99 then GOTO 900

….

…

300 ….

If y=0 the GOSUB 1200

….

900 ….

….

1200 …..

…

RETURN

GOTO 300

…..

END

1. Classical Programming.

main(){

int x,y,z;

scanf(“%d,%d”,&x,&y);

z=sum(x,y) + mul (x,y);

printf(“z=%d”,z);

}

int sum(int a,int b) {

int z;

z=a+b;

return z;

}

int mul(int a,int b) {

int z;

z=a*b;

return z;

}

2. Structured Programming.

Object Orientation is a real world approach to understand and

develop systems.

What is an object ?

An object is any thing, real or abstract, that can have properties

(data) and behavior (methods). It is an instance of a class.

3. Object Oriented Programming

Objective Thinking:

The designer thinks in terms of objects behavior not low-level

details.

Reusability:

Classes are designed so that they can be reused in many

systems (DLLs, OCXs, JARs, ..) - ( new software market).

1. Legacy Components

2. Vendor Product

3. New Software.

Why OOPs?

Interoperability:

Software from many different vendors can work together. (OMG Standards)

Ever - Growing Complex Classes:

Complex software components become building blocks for more

complex software.

Reliability:

Software built from well-proven classes is likely to have fewer

bugs than software invented from scratch.

Elements of OOP

1. Classes

2. Properties

3. Methods

4. Inheritance

5. Encapsulation

6. Messages

7. Polymorphism

8. Objects

1. Classes

In the real world, you often have many objects of the same

kind.: People, Cars, Animals, …

Using object-oriented terminology, your KIA-car object is an

instance of the class of objects known as Car.

Cars have some state (current gear, 4 wheels) and behavior

(change gears, brake) in common.

However, each car's state is independent of and can be different

from other cars.

In object-oriented software, it's also possible to have many

objects of the same kind that share characteristics:

rectangles,

employee records,

video clips

communication channels

…

A class is a blueprint or prototype that defines the variables

and methods common to all objects of a certain kind.

2. Properties

Name ………...

Color ………...

Weight …………

Birth date …………

etc ….

ID Card

A class contains data field descriptions (or properties, fields,

data members, attributes)

Field types and names, that will be associated with either per-

object or per-class state variables at program run time.

Methods implement object behavior.

They provide a means to access objects state.

A method is a sequence of instructions an object must follow

to perform a task.

3. Methods

eat run

dance run

Car

Mercedes KIA Hyundai

A-Class C-Class E-Class Accent Sonata

4. Inheritance

In object-oriented terminology:

Hyundai, KIA, and Mercedes are all subclasses of the Car class.

Similarly, the Car class is the superclass of Hyundai, KIA, and

Mercedes .

Inheritance provides a powerful and natural mechanism for

organizing and structuring software programs.

Object-oriented systems take this a step further and allow classes

to be defined in terms of other classes.

A language mechanism for restricting access to some of the

object's components

A language construct that facilitates the bundling of data with

the methods (or other functions) operating on that data.

5. Encapsulation

6. Messages

A single object alone is generally not very useful and usually

appears as a component of a larger program or application that

contains many other objects.

Software objects interact and communicate with each other by

sending messages to each other

Components Of A Message

1. The object to whom the message is addressed (Car)

2. The name of the method to perform (changeGears)

3. Any parameters needed by the method (lower gear)

Driver

Car

7. Polymorphism

RUN!

? ? ? ? ?

Robot run Bird run

Horse run

8. Objects

Objects are Things

They have state and behavior

An object is a software bundle of variables and related

methods.

Software objects are often used to model real-world objects

you find in everyday life.

A software object maintains its state in variables and

implements its behavior with methods.

Everything that the software object knows (state) and can do

(behavior) is expressed by the variables and methods within

that object.

A Sample Object

A software object that modeled your real-world car would have:

variables that indicated its current state: its speed is 90 mph,

and its current gear is the 4th gear.

The bicycle would also have methods to brake, and change

gears.

Driver

Car