Object Oriented Programming
Software Evolution:Every after decade a new software technology emerged
Since the invention of the computer many programming approaches have been tired to handle the
increasing complexity in:
 Modular programming
 Top-down approach
 Bottom-up approach
 Structured programming
Object oriented programming is an approach to program organization and development that
attempts to eliminate some of the pitfalls of conventional programming methods by incorporating
the best of structured programming features with powerful new concepts
What is Object Orientation?
The field of object orientation is to represent the objects that we find in the real world in software.
These objects may be of various types, ranging from physical to the more conceptual
Object oriented analysis method identify five types of objects
Tangible things
Physical objects eg- car, train etc
Roles
Of people or organization eg account holder, employee etc
Incidents
Something happening at a particular time eg- flight transaction etc
Interactions
A link between objects eg electrical connection, contract etc
Specifications
A definition of a set of other objects eg- a description of a particular type of
stock item etc
What is an Object?
Object are the elements through which we perceive the world around us. In other word objects are
the combination of data and function in a single unit.
We naturally see our environment as being composed of things which have recognizable
identifies and particular behaviors. All objects have these characteristics of identify and behavior
which enable us to recognize them as discrete things
Objects also exhibit state, which means that we can describe what an object is? What it does?
And what it is called?
It is instinctive to classify individual objects according to their common characteristics; we
recognize. For example that all cats are of a single type . Although we may also identify
individual different between specific cats. Our perception is that all individual cats belong to a
general class which we call cat. We know about all cats because we recognize what they have in
common
Some object are composed of other objects or contain other objects .A house object is composed
of other objects such as bricks, windows, doors, tiles etc.
Why we use objects in programs?
The world is composed of interacting, classifiable and identifiable objects and therefore programs
too, can usefully be structured in this way. Since all software application serve people living in
the real world, then that software should mirror the real world as closely as possible, both in its
workings and in its underlying design. Hence object- oriented programming is more natural way
to program then procedural programming
The object oriented programming approach to software is that it unifies inside objects two things
that have traditionally been separated in programming paradigms
 Data
 Process
Object= (private) date + public (process)
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The linking of these two aspects of programming is known as Encapsulation and allows the
implementation of information hiding
Objects have a private part of hidden internal detail (state data and internal processes) and a
public interface which clearly defines the set of possible behaviors of the objective (the message
to which it can respond). This separation of the public interface of an object and its internal
implementation allows us to treat the two as separate parts of the programming process
Why do we need object oriented programming?
 Object-oriented programming technique was developed because limitations were
discovered in earlier procedural approaches to programming
 In procedural approaches new methods in programming were introduced called structured
programming, breaking a program or list of instructions into functions. These functions
or list of instructions into functions. These functions can be further extended by grouping
a number of functions together into a module. As programs grow ever larger and more
complex even the structured programming approach begins to show signs if strain. The
reasons for the failures reveals that there are weakness in the procedural paradigm.
 In a procedural language, the emphasis is on doing things or action. The subdivision of a
program into functions continues this emphasis. Functions do things just as single
program statements do. But the data, which is an important part of the program, is given
second class status in the organization of procedural languages. ( the important part of an
inventory program isn’t a function that displays the data or a function that checks for
correct input , it’s the inventory data itself)
 The data that was probably reads from a disk file or standard input are kept in the
computer memory and treated as a variable: these variable could be declared as global or
local depending upon the nature of the programming
Features or elements of Object Oriented Language:
Objects: Object are the elements through which we perceive the world around us. Object are the
combination of data and function in a single unit. Objects can interact without having to know
details of each other’s data or code.
We naturally see our environment as being composed of things which have recognizable
identifies and particular behaviors. All objects have these characteristics of identify and behavior
which enable us to recognize them as discrete things
Objects also exhibit state, which means that we can describe what an object is? What it does?
And what it is called?
It is instinctive to classify individual objects according to their common characteristics; we
recognize. For example that all cats are of a single type. Although we may also identify individual
different between specific cats. Our perception is that all individual cats belong to a general class
which we call cat. We know about all cats because we recognize what they have in common
Some object are composed of other objects or contain other objects .A house object is composed
of other objects such as bricks, windows, doors, tiles etc.
Class: Class is a blue print of an object. In other word class is a collection of objects, where user
can define data and related functions to manipulate the data. For example manager, peon is the
object of the class employee and car, bus is the object of the class vehicle.
It specifies what data and functions will be included in objects of that class. Defining class
doesn’t create an object but class is the description of object’s attributes and behaviors
Class: person
Attributes: Name, sex, age etc
Behaviors: Speak ( ), Listen ( ), Walk ( )
When class is defined, objects are created as
<Class name><object name>;
If employee has been defined as a class, then the statement
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Employee manager;
Will create an object manager belonging to the class employee.
Each class describes a possibly infinite set of individual objects, each object is said to be an
instance of its class and each instance of the class has its own value for each attribute but shares
the attribute name and operations with other instances of the class. The following points give the
idea of the class:
A class is a template that unites data and operations.
A class is an abstraction of the real world entities with similar properties
A class is an implementation of abstract data type.
Inheritance
Inheritance is the process by which objects of one class inherits the characteristics of another
class as part of its definition. It supports the concept of hierarchical classification
Inheritance is appropriate when one class is a kind of other class (text window is a kind of
window)
In OOP, the concept of inheritance provides the idea of reusability; we can add additional features
to an existing class without modifying it. This process, deriving a new class from the existing one
is called inheritance
Once a class has been written and debugged, it can be distributed to different programmers for
reuse, which is called reusability in object-oriented programming. A programmer can take class
and without modifying it, can add new features and create a new class according to the
requirements. This can be done by deriving a new class from the existing one. The new class will
inherit the capabilities of the existing one, but it is free to add new features of its own. Code
reusability is one of the major advantages of inheritance.
Polymorphism
The word polymorphism is derived from Latin words ‘poly’ means many and ‘morphos’ means
form.So, polymorphism means “having many forms”. The polymorphism allows different
objects to respond to the same message in different ways, the response specific to the type of
objects. Polymorphism is important when object oriented programs dynamically creating and
destroying the objects in run time. Example of polymorphism in OOP is operator overloading,
function overloading.
For example:- operator symbol ‘+’ is used for arithmetic operation between two numbers,
By overloading same operator ‘+’ can be used for concatenation of strings.
Data Abstraction and Encapsulation: - The wrapping up of data and function into a single unit
is called encapsulation. Encapsulation is the most striking feature of a class . The data is not
accessible from outside of class. Only member function can access data on that class. The
prevention of data from direst access by the program is called data hiding. That data can be
hidden making them private so that it is safe from accidental modification.
Abstraction is the representation of all the essential features (state and behaviors) of an object
without including the details or explanations. The classes use the concept of data abstraction, so
they are known as abstract data types (ADT)
Applicatons of OOP
 OOP has become one of the programming buzzword today
 Applications of OOP are beginning to gain importance in many areas
 The most popular application of OOP has been in the area of user interface design such as
windows. There are hundreds of windowing systems developed using OOP techniques
 Real-business systems are often much more complex and contain many more objects with
complicated attributes and methods (member functions). OOP is useful in this type of
applications because it can simplify a complex problem
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 The promising areas for application of OOP includes:
 Games
 Expert system
 Object-oriented databases
 Artificial Intelligence
 AI and expert systems
 Most important areas of application is design of user interface
such as window
 Computer based training and educational systems
 OO technology is going to change the way software engineers will think, analysis, design
and implement systems in future
Comparison between Procedural and OO programming
Procedural
Date type
Variable
Function/Procedure
Function calls
Problem is divided into different
functions
6. Follow top down approach
7. Emphasis is given on procedures rather
than data
8. It allow data to move freely by
declaring data globally
1.
2.
3.
4.
5.
Object- oriented
Abstract data type/ class
Object/Instance
Method/ Operation/ Service
Message passing
Problem is divided into different
objects
6. Follow bottom up approach
7. Emphasis is given on data rather than
Procedure
8. It does not allow data to move freely
by making data private
1.
2.
3.
4.
5.
Important features of Object-Oriented Programming are as follows:1) Emphasis is given on data rather than procedures
2) Programs are divided into different groups known as objects
3) Data structures are designed such that they characterize the objects
4) Functions and data are tied together
5) Data is hidden and can’t be accessed by external function
6) Functions are communicated between each other through objects.
7) New data and function can easily be added
8) Follow Bottom up approach
Important features of procedure-oriented programming are as follows:1) Emphasis is on doing things rather than data
2) Large programs are divided into smaller programs know as function
3) Data move freely around the program from function to function
4) Function transforms data from one form to another
5) Employs top-down approach in program desi
Advantages and disadvantages Object-Oriented Programming:OOP contributes greater programmer productivity Better quality of software and lesser
maintenance cost. The main advantages are:1) Making the use of inheritance, redundant code is eliminated and the existing class is
extended
2) Through data hiding programmer can build secure programs that cannot be invaded by
code in other parts of the program
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3) System can be easily upgraded from small to large systems
4) Software complexity can be easily managed
5) Message passing technique for communication between objects makes the interfaces
description with external system much simpler
6) Code reusability is much easier than conventional programming language
Disadvantage of OOP
1) Compiler and runtime overhead. Object oriented program required greater processing
overhead demands more resources
2) An object’s natural environment is in RAM as dynamic entity but traditional data storage
in files or databases
3) Requires the mastering in software engineering and programming methodology
4) Benefits only in long run while managing large software projects
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