Basic Object Oriented Concepts

Name: VINOD PILLAI

Email: vinodthebest@gmail.com

Object Oriented Programming

Developments in software technology continue

to be dynamic.

This maid the software industry and software

engineers to continuously look for new

approaches to software design and

development.

Rapid advances appear to have created a

situation of crisis within the industry.

Object Oriented Programming

Major issues need to resolved:

How to represente real-life entites

How to ensure reusability and extensibility of

modules

How to develop modules that are tolerant to any

changes in future

How to improve software productivity and decrease

software cost

How to improve the quality of software

How to manage time schedules

Object Oriented Programming

Studies and other reports on software

implementation suggest that software products

should be evaulated carefully for their quality

before they are delivered and implemented.

Software Evolution

To built todays complex software it is just not

enough to put together a squence of

programming statements and sets of

procedures and modules; we need to

incorporate sound construction techniques and

program structures that are easy to

comprehend, implement and modify.

Since the invention of the computer, many

programming approaches have been tried.

Software Evolution

Such as Modular programming, top-down

programming, bottom-up programming and

structured programming.

The primary motivation in each case has been

the concern to handle the increasing complexity

of programs that are reliable and maintainable.

C vs C++

C Structured programming became very

popular and was the main technique of the

1980.

Structured programming enable programmers

to write moderately complex programs fairly

easily.

However as the programs grew larger, even the

structured approach failed to show the desired

results in terms of bug-free, easy-to-maintain

and reusable programs.

C vs C++

C++ - Object-Oriented Programming (OOP) is

an appraoch to program organization and

development that attempts to elimate some of

the pitfalls of conventional programming

methods by incorporating the best of structured

programming features with several powerful

new concepts.

Procedure-Oriented Programming

Conventional programming using high level

language such as COBOL, FORTRAN and C is

commonly known as Procedure-oriented

programming.

In the Procedure-oriented approach the

problem is viewed as a sequence of things to

be done such as reading, calculating and

printing.

The primary focus is on functions.

Structure of Procedure-oriented

Main Program

Function 1 Function 2 Function 3

Function 5Function 4

Procedure-Oriented Programming

Procudure-oriented programming basically

consists of writing a list of instructions for the

computer to follow and organizing these

instructions into groups known as functions.

We normally use a flowchart to organize these

actions and represent the flow of control from

one action to another.

More importance to functions very little attention

to data that are being used by the functions.

Structure of Procedure-oriented

Global data

Function 2

Global data

Function 3Function 1

Local data Local data Local data

Procedure-Oriented Programming

What happens to data? How are they affected

by the functions that work on them?

In multi-function program many important data

items are placed as global so that they may be

accessed by all the functions.Each function may

have its own local data.

In large program it is very difficult to identify

what data is used by which function. In case we

need to revise an external data structure we

also need to revise all function that access it.

Object-Oriented Programming

OOP treats data as a critical element in the

program development and does not allow it to

flow freely around the system.

It ties data more closely to the functions that

operate on it, and protects it from accidental

modification from outside functions.

OOP allows decomposition of a problem into a

number of entites called objects.

Organization of data & function OOP

Data

Functions

Object A

Data

Functions

Object B

Data

Functions

Object C

Object A Object B

Striking features of OOP

Emphasis is on data rather than procedure.

Programs are divided into what are known as objects

Functions that operate on the data of an object are

tied together in the data structure

Data is hidden and cannot be accessed by external

functions

Objects may communicate with each other through

functions

New data and functions can be easily added whenever

necessary.

Object-oriented programming

Object-oriented programming is an approach that

provides a way of modularizing programs by creating

partitioned memory area of both data and fucntions

that can be used as templates for creating copies of

such modules on demand.

Object is considered to be a partitoned area of

computer memory that stores data and set of

operations that can access that data.

Basic concepts of OOP

Objects

Class

Data Abstration

Data Encapsulation

Inheritance

Polyomorphism

Dynamic binding

Message Passing

The three pillars of object-oriented development:

Encapsulation, Inheritance, and Polymorphism.

Objects

Objects are the basic run-time entities in an object-

oriented system.

They may represent a person, a place, a bank

account, a table of data or any item that the program

must handle.

Program objects should be chosen such that they

match closely with the real-world objects.

Objects take up space in the memory and have an

associated address like sturcture in C.

When a program is executed the objects interact by

sending messages to one another.

Objects

Ways to represent an Object

Object: STUDENT

DATA

Name

Marks

FUNCTIONS

Total

Display

Classes

The entire set of data and code of an object can be

made a user-defined data type with the help of a class.

Objects are variable of type class.

Once a class has been defined we can create any

number of objects belonging to that class.

A class is thus a collection of objects of similar type.

Classes are user-defined data types and behave like

the built-in types of a programming language.

Classes

Syntax used to create an object is no different than the

syntax used to create an integer object in C.

Fruit is a class defined as a Class.

fruit f1;

Here fruit is Class.

And f1 is an object of fruit Class.

Encapsulation

The wrapping up of data and functions into a single

unit is known as Encapsulation

The data is not accessible to the outside world and

only those functions which are wrapped in the class

can access it.

This insulation of the data from direct access by the

program is called data hiding or information

hiding.

Data Abstraction

Abstraction refers to the act of representing essential

features without including the background details or

explanations.

Classes use the concept of abstraction and aredefined as a list of abstract attributes such as size,

weight and cost, and functions to operate on these

functions.

Since the classes use the concept of data

abstraction, they are known as Abstract Data

Types.

Inheritance

Inheritance is the process by which objects of one

class acquire the properties of objects of another

class.

The principle behind this sort of division is that each

derived class shares common characteristics with the

class from which it is derived.

In OOP the concept of inheritance provides the

idea of reusability.

This means that we can add additional features to an

existing class without modifying it.

Inheritance

The real power of inheritance mechanism is that it

allows the programmer to reuse a class that is almost

but not exactly, what he wants, and to tailor the class

in such a way that it does not introduce any

undesirable side-effects into the rest of the classes.

Bird

Flying Bird No flying Bird

Polymorphism

Polymorphism means the ability to take more than one

form.

That is an operation may exhibit different behaviours

in different instances. The behaviour depends upon

the types of data used in the operation.

Example: Operation of addition.

For two numbers the operation will generate a sum. If

the operands are strings, then the operation would

produce a third string by concatenation.

Polymorphism

The process of making an operator to exhibit different

behaviours in different instances is known as

operator overloading.

Using a single function name to perform different types

of taks is known as function overloading.

Dynamic Binding

Binding refers to the linking of a porcedure call to the

code to be executed in response to the call.

Dynamic binding means that the code associated with

a given procedure call is not known until the time of

the call at run-time

It is associated with polymorphism and

inheritance.

Message Communication

An object-orineted program consits of a set of objects

that communicate with each other.

Object communicate with one another by sending and

receiving information much the same way as people

pass message to one another.

Message passing involves specifying the name of the

object, the name of the funciton (message) and the

information to be sent.

emp.salary(emp_name);

objectmessage

information

Benefits of OOP

Through inheritance we can elimate the redundant

code and extend the use of existing code

Data hiding helps the programmer to build secure

programs that cannot be invaded by code in other

parts of the program

It is possible to have mulitple instances of an objects

to co-exist without any interference.

It is possible to map objects in the problem domain to

those objects in the program

Easy to partition the work in a project based on objects

Benefits of OOP

Data-centred design approach enables us to capture

more details of a model in implementable form

Object-oriented systems can be easily upgraded from

small to large systems

Software complexity can be easily managed.

Object-Oriented Languages

The lanugages should support several of the OOP

concepts to claim that they are object-oriented.

Depending upon the features they support, they can

be classified into the following two categories:

Object-based programming lanugages

Object-oriented programming languages

Object-based programming Languages

Object-based programming is the style of

programming that primarily supports encapsulation

and object identify.

Major features:

Data encapsulation

Data hidding and access mechanisms

Automatic initialization and clear-up objects

Operator overloading

They do not support inheritance and dynamic

binding.

Object-oriented programming Languages

Object-oriented programming incorporates all of

object-based programming features along with two

additional features, namely, iheritance and dynamic

binding.

Object-based features + inheritance + dynamic binding

References

Object-Oriented Programming with C++ by E

Balagurusamy