USIT201-Object-Oriented-Programming-munotes

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1OBJECTS ORIENTED METHODOLOGY
Chapter Structure :
1.0 Program and Programming
1.1 Programming Languages
1.2 Procedure Oriented Programming
1.3 Need of Object Oriented Programming
1.4 Object Oriented Programming
1.5 Comparison of Procedural and Object Oriented Approach
1.6 Benefits of OOP
1.7 Advantages of OOPs
1.8 Object Oriented Languages
1.9 Applications of OOPS
1.10 Question
1.0 Program and Programming
Components of any computer system are hardware and software.
Both hardware and software have their own sets of functionalities which can
be interdependent or independent of each other.
A computer system is designed to produce the desired results by making the
functionalities of both the hardware and the software to converge.
The hardware is what we can see, touch and feel e.g. keyboard, mouse, visual
display units like monitors, printers etc.
The software can be modified / replaced with lesser effort, time and money.
Computer is essentially a data processing machine which requires two kinds
of inputs for its operations and these are: data and instructions.
The hardware of a computer can not produce the desired results unless it is
given the requisite instructions and data by the user(s).
Do you know what is software all about? The software deals with the
instructions.
The examples of software are Microsoft Office, Microsoft Windows 7, Red
Hat Linux, Railways Reservation System, Microsoft Internet Explorer,
Google Search Engine etc.
A program as an independent entity or as part of a software is intended to
instruct the hardware to carry out specific task(s) to the satisfaction of the
user(s) by providing specific outcomes. So how do you define a program?1UNIT – I
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2OBJECT ORIENTED PROGRAMMING
A program can be defined to be a set of instructions written in a programming
language which are given in a fixed sequence to the hardware of a specific
computer and executed by its hardware to produce predetermined and
expected outcomes.
The instructions in a program are written mostly in natural languages (e.g.
English, Hindi, French, German, and Chinese etc.) following the syntax (form)
and semantics (meaning) of the programming language chosen for writing
the program.
There are a variety of programming languages available for writing the
programs e.g. BASIC, C, C++, Java, Prolog, Lisp, HTML, PHP etc. The
sequence of instructions is very important because if the sequence is not
correct, the expected results cannot be achieved by the program.
Now, let us see what does programming mean to us? The meaning of the
term programming (or computer programming) has been changing rapidly
since the idea of a first program was envisaged.
Initially the computers were used to solve the mathematical problems with
the help of calculations.
Hartee in 1950 suggested that the process of preparing a calculation for a
machine can be broken down into two parts, ‘programming’ and ‘coding’.
He described programming as the process of drawing up the schedule of the
sequence of individual operations required to carry out the calculation.
In 1958, Booth proposed that the process of organizing a calculation can be
divided into two parts, a) the mathematical formulation, and b) the actual
programming. With the passage of time, the definition of programming has
kept on evolving and at present programming is considered to be the process
of writing programs and may include activities as diverse as designing,
writing, testing, debugging and maintaining the code of a program.
In normal conversation, programming is described as the process of instructing the
computer to do something desired and useful for the user with the help of a
programming language.
1.1 Programming Languages
The programming languages are created by, we, human beings.
These languages are used to communicate instructions to the machines
especially computers so that the programs can control the behaviour of the
hardware of the machines to get desired results.
Basically, the hardware of the computers understands only the language of
the hardware which is called the machine language.
The hardware is unable to understand and decipher any program written in
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3Every type of a CPU has its own machine language.
Therefore, in order to make the hardware of a computer understand the
instructions contained in a program written in any other programming
language, a mechanism called ‘translator’ is required.
This translator converts the program written in programming languages other
than the native machine language of the CPU (hardware) into the native
machine language of a particular CPU on which this program is intended to
be executed.
Every programming language must have its own translator for the programs
written in it to be executed or run on the computer hardware.
Various types of translators available can be categorized into assemblers,
interpreters or compilers.
The primitive or the first generation of programming languages were called
machine languages and the symbols like ‘0’ and ‘1’ were used to write
programs under this category of programming languages.
The second generation of programming languages were called the assembly
languages and mainly used mnemonics to construct a program.
The third generation of programming languages was called high level
languages as these programming languages were independent of the CPU of
the hardware being used and the instructions written in the programs were
just like the instructions given in natural languages.
The third generation languages are known as 3GL languages.
The current generation of the programming languages are called the fourth
generation languages or the 4GLs. These languages represent the class of
programming languages that are closest to the human (natural) languages.
Based on the intended use of domain of use, the programming languages are
broadly classified as imperative programming languages where imperative
sentences are used in a program to issue commands in terms of instructions;
and declarative programming languages where declarative instructions are
used in a program to assert the desired result.
More common paradigm classifies these languages into imperative,
functional, logic programming and object-oriented languages.Chapter 1 : Objects Methodology
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4OBJECT ORIENTED PROGRAMMING
Following Table presents the summary of main features of these programming
paradigms.
Paradigm Key Key Concepts Program Result
Concepts Execution
Functional Function Collection of Evaluation of Value of the
functions functions main function
Imperative Command Sequence of Execution of Final state of
(instruction) commands commands computer
memory
Logic Predicate Logic formulas: Logic proving Failure or
axioms & a of the theorem Success of
theorem proving
Object- Object Collection of Exchange of Final state
oriented classes of objects messages of the objects
between the
objects
1.2 Procedure Oriented Programming
Conventional programming language using high level language such as Cobol
and C, is commonly known as Procedure Oriented Programming (POP).
In Procedure Oriented Programming, the problem is viewed as a sequence
of a thing to be done.
The primary focus is on functions.
Procedure Oriented Programming basically consists of writing a list of
instructions for the computer to follow, and organizing these functions into
groups known as functions.
In a 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.
Some characteristics of Procedure Oriented Programming are:
1. Large programs are divided into smaller programs known as functions.
2. Most of the functions share global data.
3. Data move openly around the system from function to function.
4. Functions transform data from one form to another.
5. Employs top-down approach in program design.munotes.in

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51.3 Need of Object Oriented Programming
Developments in software technology continue to be dynamic. New tools
and techniques are announced in quick succession.
This has forced the software engineers and industry to continuously look for
new approaches to software design and development, and they are becoming
more and more critical in view of the increasing complexity of software
system as well as the highly competitive nature of the industry.
This rapid advance appears to have created a situation of crises within the
industry.
The following issues needs to be solved:
•To represent real life entities of problems in system design.
•To design system with open interface.
•To ensure reusability and extensibility of modules.
•To develop modules that is tolerant to any changes in future
•To improve software productivity and decrease cost.
•To improve the quality of the software.
•To manage time schedule.
•To industrialize the software development process.
To overcome these problems and major motivation factor in the invention of object
oriented approach is to remove some of the flows encountered in the procedure
oriented approach.
1.4 Object Oriented Programming
Object Oriented Programming is the most recent concept among programming model.
The motivating factor in the invention of object oriented approach is to remove
some of the flows encountered in the procedural approach. OOPS treats data as a
critical element in the program development and does not allow it to flow freely
around the system. It binds data more closely to the functions that operate on it, and
protects it from accidental modification from outside functions.
Some of the striking features of Object Oriented Programming are:
•Importance on data rather than procedure.
•Programs are divided into what are known as objects.
Data structures are designed as such that they characterize the objects.
Introduction to OOPs
•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.
•Follow bottom-up approach in program design.Chapter 1 : Objects Methodology
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6OBJECT ORIENTED PROGRAMMING
Sr.
NoProcedure Oriented Programming Object Oriented Programming
POP is divided into small parts
called as functionsIn OOP, program is divided into
parts called objects
In POP, Importance is not given to
data but to functions as well as
sequence of actions to be done.In OOP, Importance is given to
the data rather than procedures or
functions because it works as a
real world.
POP follows top-down approach. OOP follows bottom-up approach.
POP does not have any access
specifier.OOP has access specifiers named
Public, Private, Protected, etc.
In POP, data can move freely from
function to function in the system.In OOP, objects can move and
communicate with each other
through member functions.
To add new data and function in
POP is not so easy.OOP provides an easy way to add
new data and function.
In POP, most function uses global
data for sharing that can be accessed
freely from function to function in
the system.In OOP, data cannot move easily
from function to function, it can be
kept public or private so we can
control the access of data.
POP does not have any proper way
for hiding data so it is less secure.OOP provides data hiding so
provides more security.
In POP, overloading is not possible. In OOP, overloading is possible in
the form of Function Overloading
and Operator Overloading.
Example of POP are: C, VB, FOR-
TRAN, Pascal.Example of OOP are: C++, JA V A,
VB.NET, C#.NET.1.5 Comparison of Procedural and Object Oriented Approach
There are two different approaches to write a program, i.e., Procedure Oriented
Programming and Object Oriented Programming. Basic aim of these methods is
nothing but to make programming efficient. We can write the program using any of
the way but there are notable differences between both approaches.
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71.6 Benefits of OOP
1) As OOP is closer to the real world phenomena, hence, it is easier to map real
world problems onto a solution in OOP.
2) The objects in OOP have the state and behaviour that is similar to the real
world objects.
3) It is more suitable for large projects.
4) The projects executed using OOP techniques are more reliable.
5) It provides the bases for increased testability (automated testing) and hence
higher quality.
6) Abstraction techniques are used to hide the unnecessary details and focus is
only on the relevant part of the problem and solution.
7) Encapsulation helps in concentrating the structure as well as the behaviour of
various objects in OOP in a single enclosure.
8) The enclosure is also used to hide the information and to allow strictly controlled
access to the structure as well as the behaviour of the objects.
9) OOP divides the problems into collection of objects to provide services for
solving a particular problem.
10) Object oriented systems are easier to upgrade/modify.
11) The concepts like inheritance and polymorphism provide the extensibility of
the OOP languages.
12) The concepts of OOP also enhance the reusability of the code written.
13) Software complexity can be better managed.
14) The use of the concept of message passing for communication among the objects
makes the interface description with external system much simpler.
15) The maintainability of the programs or the software is increased manifold. If
designed correctly, any tier of the application can be replaced by another
provided the replaced tier implements the correct interface(s). The application
will still work properly.
1.7 Advantages of OOPs
1. Code reusability in terms of inheritance.
2. Object-oriented system can be easily upgraded from one platform to another.
3. Complex projects can be easily divided into small code functions.
4. The principle of abstraction and encapsulation enables a programmer to build
secure programs.
5. Software complexity decreases.
6. Principle of data hiding helps programmer to design and develop safe programs.
7. Rapid development of software can be done is short span of time.
8. More than one instance of same class can exist together without any interference.Chapter 1 : Objects Methodology
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8OBJECT ORIENTED PROGRAMMING
1.8 Object Oriented Languages
Some of the most popular Object-oriented Programming languages are :
a)C++
b)Ruby
c)Java.
d)Delphi
e)smalltalk
f) Charm++
g)Eiffle.
h)Simula.
1.9 Applications of OOPS
Object concept helps to translate our thoughts to a program. It provides a way of
solving a problem in the same way as a human being perceives a real world problem
and finds out the solution. It is possible to construct large reusable components
using object-oriented techniques. Development of reusable components is rapidly
growing in commercial software industries. If there is complexity in software
development, object-oriented programming is the best
paradigm to solve the problem. The following areas make the use of OOP:
1. Image Processing
2. Pattern Recognition
3. Computer Assisted Concurrent Engineering
4. Computer Aided Design and Manufacturing
5. Computer Aided Teaching
6. Intelligent Systems
7. Database Management Systems
8. Web-based Applications
9. Distributed Computing and Applications
10. Component-based Applications
11. Business Process Re-engineering
12. Enterprise Resource Planning
13. Data security and management
14. Mobile Computing
15. Data Warehouse and Data Mining
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91.10 Questions
Q1. Why does hardware not provide flexibility of operations to the user ?
Q2. How is a program related to software?
Q3. What is the signature of a method?
Q4. Differentiate between information hiding and encapsulation.
Q5. What is the difference between object-oriented and object-based programming
languages?
Q6. What is the need of Object Oriented Programming ?
Q7. Differentiate Procedure Oriented Programming & Object Oriented
Programming
Q8. List and explain benefits of OOP .
Q9. List and explain application of OOPS
*****Chapter 1 : Objects Methodology
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10OBJECT ORIENTED PROGRAMMING
2
PRINCIPLES OF OOPS
Chapter Structure :
2.0 Object Oriented Programming Paradigm
2.1 Characteristics of OOPS / Concepts of OOPS
2.1.0 Class
2.1.1 Object
2.1.2 Polymorphism
2.1.3 Inheritance
2.1.4 Reusability
2.1.5 Data abstraction and encapsulation
2.1.6 Dynamic Binding
2.1.6 Message Passing
2.2 Summary
2.3 Further Readings
2.4 Web Reference
2.5 Questions
2.0 Object Oriented Programming Paradigm
Simula was the first programming language developed in the mid-1960s to
support the object-oriented programming paradigm followed by Smalltalk
in the mid-1970s that is known to be the first ‘pure’ object-oriented language.
Eiffel, Java, C++, Object Pascal, Visual Basic, C# etc are the other OOP
languages that came into existence later on, all having different complexities
of syntax and dynamic semantics.
The main motive of the developers of programming languages over the years
has always been to create such programming languages that are close to
human (i.e. natural) languages.
The way we perceive and interact with the things in our day-to-day lives, the
representation of programming constructs should closely match the same.
Hence came into existence the concept of ‘objects’ and ‘object-oriented
programming paradigm’.
Every object has certain defining properties which distinguish it not only
from different types of other objects but from the similar types of objects
too.
Every object has certain functions associated with it and all similar types of
objects are supposed to support these. Although, Some of these functions
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11Chapter 2 : Principles of OOPS
Example with Explanation : In case of a ball pen, one of the functions
associated with each type of ball pen object, is to write and another associated
function is the provision to hold it in hands conveniently. All the ball pen
objects support both these functions. Incidentally, all the tooth brush objects
also support the function of holding them in the hands conveniently but, in
addition, support other functions like brushing the teeth too.
This concept of objects borrowed from the real world has been the basis of
the object-oriented programming (OOP) paradigm and this paradigm is a
direct consequence of an effort to have a programming language closely
matching the human behaviour.
 This OOP paradigm is all about creating program(s) dealing with objects
where these objects interact with one another to achieve the overall objectives
of the program. Every object in the programs has certain defining properties
called attributes (or instance variables) possessing supporting values for each
of the attributes and some associated functions (normally called methods or
operations). As in the real world objects, no two objects in a program can
have the same values of all the attributes.
At times, instead of dealing with individual objects, it is convenient to talk
collectively about a group of similar objects where all the objects of this
group will have the same set of attributes and methods.
In the object-oriented programming paradigm parlance, this collection of
objects corresponding to a particular group is known as a class.
All programs under this paradigm contain a description of the structure
(corresponding to attributes) and behaviour (corresponding to methods) of
so called classes.
In a program, various objects are created from these classes. The process of
creation of an object from a class is called ‘instantiation’ and the object created
is known as an instance of the class.
Every object created will have a ‘state’ associated with the description of the
structure in the class from which it has been instantiated.
The state of an object is defined by the set of values assigned to its
corresponding attributes (and stored in the memory) of the object.
A class is defined to be a template or a prototype so that a collection of
attributes and methods can be described within it and this definition can be
used for creating different objects within a program.
It is this concept of encapsulating the data and methods within the objects
that provides the programmers with flexibility within the OOP paradigm
because an object can be extended or modified without making changes to
its external interface or other classes/objects in the program.
Various classes may exhibit features like inheritance and polymorphism of
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12OBJECT ORIENTED PROGRAMMING
2.1 Characteristics of OOPS / Concepts of OOPS
Characteristics of OOPs are :
Object
Classes
Polymorphism
Inheritance
Reusability
Data abstraction and encapsulation
Dynamic Binding
Message Passing
2.1.0 Class
A group of objects that share common properties for data part and some
program part are collectively called as class.
In C ++ a class is a new data type that contains member variables and member
functions that operate on the variables.
The most remarkable feature of C + + is a class. The class binds together
data and methods which work on data. The class is an abstract data type
(ADI) so creation of class simply creates a template.
The class is a keyword.
The general syntax of creating a class in C++ is given below:munotes.in

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13class class name
{
public :
data & function;
private :
data & function;
protected :
data & function;
};
Following this keyword class, class_name represents name of the class. The class
name must obey rules of writing identifier as class_name is nothing but an identifier.
The class is opened by opening brace} and closed by closing brace}. The class
definition/declaration must end with semicolon. Inside the class we define the data
members and member functions. They may be defined either public, private or jn
protected mode.
There are three different types of mode :
1. public
2. private
3. protected.
2.1.1 Object
Objects are the basic run time entities in an Object Oriented System.
 They may represent a person, a bank account, a table of data or any item
that the program has to handle.
They may also represent user-defined data such as vector, time, and lists.
When a program is executed, the objects interact by sending messages to
one another.
Creating objects is similar to declaring variables.
Syntax: