JIMS Vasant Kunj-II, BCA Department of Information Technology teaches all object Oriented and Object Based Languages. It provides the best BCA Course in Delhi. Every Year the BCA department ensures to provide best curriculum and tries to keep updated the students with all concepts in depth. The BCA faculties tries to make the base strong of all students and take them to the depth of the subject.
Technology has
upgraded itself in always but still the object-oriented paradigm is used by all
languages in demand. To implement the features of various object-oriented Languages,
it is required to understand the OOP’s paradigm.
Object
oriented programming is a concept that was created because of the
need to overcome the problems that were found with using structured programming
techniques. While structured programming uses an approach which is top down,
OOP uses an approach which is bottom up. Object oriented programming emphasis
on objects and information or classes. With object-oriented programming, a
problem will be broken down into a number of units. These units are called
objects
The object-oriented
(OO) analysis and paradigm is well understood from the initial concept of a programming
approaches and the implementation is the logical result of the wide adoption of
OO programming languages.
History
of Object-Oriented Programming- a new paradigm
|
Year |
Details |
|
1983- Bjarne
Stroustrup |
Posted the ideas of
Simula to C to support Simulation Programming with Classes i.e., C++ |
|
1984- Brad Cox |
Added Smalltalk style
messages, passing Syntax to C, Called it Objective C |
|
1995- James Gosling |
Created Java,
Integrated implementation technology from Smalltalk and Syntax from C++ |
|
2000- Anders Hejlsberg |
Created C#, The main
language of .NET platform from Microsoft |
History
of Object-Oriented Programming Languages
|
Language |
Development Year |
Remarks 1 |
Remarks 2 |
|
Simula-First OOP’s
Language |
1960 |
Used for Simulation
of Real Systems |
Researchers at
Norwegian Computing Center |
|
Smalltalk |
1970 |
First Pure Object-Oriented
Programming language developed for Dynabook |
Dynabook was a
Personal Computer created by Alan Kay and his research Group at Xerox PARK |
|
Ada |
1980 |
Grady Booch
published a paper titled Object Oriented Design |
In this paper he
presented a design for the programming language, Ada Later on, he
extended his ideas to a complete object–oriented design method |
|
Language is
incorporated with Behavioral ideas to Object Oriented Methods |
1990 |
Coad incorporated
behavioral ideas to object-oriented methods
|
|
|
Object Modeling
Techniques |
1991-James Rumbaugh,
Blaha, Premerlani, Eddy and Lorenzen |
Method to
develop object-oriented systems and to support object-oriented
programming. |
It is an object
modelling approach for software modelling & designing |
|
Object Oriented
Software Engineering |
1992 |
Ivar Jacobson |
software
design technique that is used in software
design in object-oriented programming. |
Introduction
to OO Paradigm
OO paradigm is a
significant methodology for the development of any software. Most of the
architecture styles or patterns such as pipe and filter, data repository, and
component-based can be implemented by using this paradigm.
Object
means a real word entity which can be defined in terms of its data members and
Member Functions. Object-Oriented Programming is a methodology or paradigm to
design a program using classes and objects. It simplifies the software
development and maintenance by providing some concepts:
•
Object
•
Class
•
Data Encapsulation
•
Data Abstraction
•
Inheritance
•
Polymorphism
•
Dynamic Binding
•
Message Passing
Basic concepts and
terminologies of object–oriented systems are defined as−
OBJECT
•
Objects are basic building blocks for
designing programs.
•
An object is a collection of data
members and associated member functions.
•
An object is an instance of a class.
•
Each object is identified by a unique
name. Each object must be a member of a particular class.
•
An object is the entity that is created
to allocate memory.
•
A class when defined does not have memory
chunk itself which will be allocated as soon as objects are created.
•
For example: An object may represent a
person, place or a table of data chair, pen, table, keyboard, bike etc. It can
be physical and logical entity.
•
Syntax
Objects can be modeled
according to the needs of the application. An object may have a physical
existence, like a customer, a car, etc.; or an intangible conceptual existence,
like a project, a process, etc.
CLASS
A class is a data-type that has its own
members i.e., data members and member functions It gives the blueprint or the description of the objects that
can be created from it. Creation of an object as a member of a class is called
instantiation. Thus, an object is an instance of a class.
Some
important properties of class are −
▰
Class is a user-defined data-type.
▰
A class contains members like data
members and member functions.
▰
Data members are variables of the class.
▰
Member functions are the methods that
are used to manipulate data members.
▰
Data members define the properties of
the class whereas the member functions define the behaviour of the class.
A class can have
multiple objects which have properties and behaviour that in common for all of
them.
Example
Let us consider a
simple class, Circle, that represents the geometrical figure circle in a
two–dimensional space. The attributes of this class can be identified as
follows −
- x–coord, to denote x–coordinate
of the center
- y–coord, to denote y–coordinate
of the center
- a, to denote the radius of the
circle
Some of its operations
can be defined as follows −
- findArea (), a method to
calculate area
- findCircumference (), a method
to calculate circumference
- scale (), a method to increase
or decrease the radius
ENCAPSULATION
Encapsulation is the process of binding both attributes and
methods together within a class. Through encapsulation, the internal details of
a class can be hidden from outside. It permits the elements of the class to be
accessed from outside only through the interface provided by the class.
POLYMORPHISM
Polymorphism is originally a Greek word that means the ability
to take multiple forms.
▰
Poly – many
▰
Morphos - forms.
In object-oriented paradigm, polymorphism implies using
operations in different ways, depending upon the instances they are operating
upon. Polymorphism allows objects with different internal structures to have a
common external interface. Polymorphism is particularly effective while
implementing inheritance.
The
ability of an operator and function to take multiple forms is known as Polymorphism.
It allows a single object, method, operator associated with different meaning
depending on the type of data passed to it. The different types of polymorphism
are
·
Operator overloading
· Function
overloading.
Let us consider two
classes, Circle and Square, each with a method findArea (). Though the name and
purpose of the methods in the classes are same, the internal implementation,
i.e., the procedure of calculating an area is different for each class. When an
object of class Circle invokes its findArea () method, the operation finds the
area of the circle without any conflict with the findArea () method of the
Square class.
Relationships
In order to describe a
system, both dynamic (behavioral) and static (logical) specification of a
system must be provided. The dynamic specification describes the relationships
among objects e.g., message passing. And static specification describes the
relationships among classes, e.g., aggregation, association, and inheritance.
MESSAGE PASSING
Any application requires a number of objects interacting in a
harmonious manner. Objects in a system may communicate with each other by using
message passing. Suppose a system has two objects − obj1 and obj2. The object
obj1 sends a message to object obj2, if obj1 wants obj2 to execute one of its
methods.
COMPOSITION OR AGGREGATION
Aggregation or composition is a relationship among classes by
which a class can be made up of any combination of objects of other classes. It
allows objects to be placed directly within the body of other classes.
Aggregation is referred as a “part–of” or “has–a” relationship, with the
ability to navigate from the whole to its parts. An aggregate object is an
object that is composed of one or more other objects.
ASSOCIATION
Association is a group of links having common structure and
common behavior. Association depicts the relationship between objects of one or
more classes. A link can be defined as an instance of an association. The Degree
of an association denotes the number of classes involved in a connection. The
degree may be unary, binary, or ternary.
- A unary relationship connects
objects of the same class.
- A binary relationship connects
objects of two classes.
- A ternary relationship connects
objects of three or more classes.
INHERITANCE
It is a mechanism that permits new classes to be created out of
existing classes by extending and refining its capabilities. The existing
classes are called the base classes/parent classes/super-classes, and the new
classes are called the derived classes/child classes/subclasses.
The subclass can
inherit or derive the attributes and methods of the super-class (es) provided
that the super-class allows so. Besides, the subclass may add its own
attributes and methods and may modify any of the super-class methods.
Inheritance defines a “is – a” relationship.
Example
From a class Mammal, a
number of classes can be derived such as Human, Cat, Dog, Cow, etc. Humans,
cats, dogs, and cows all have the distinct characteristics of mammals. In
addition, each has its own particular characteristics. It can be said that a
cow “is – a” mammal.
OO
Analysis
In object-oriented
analysis phase of software development, the system requirements are determined,
the classes are identified, and the relationships among classes are
acknowledged. The aim of OO analysis is to understand the application domain
and specific requirements of the system. The result of this phase is
requirement specification and initial analysis of logical structure and
feasibility of a system.
The three analysis
techniques that are used in conjunction with each other for object-oriented
analysis are object modeling, dynamic modeling, and functional modeling.
OBJECT MODELING
Object modeling develops the static structure of the software
system in terms of objects. It identifies the objects, the classes into which
the objects can be grouped into and the relationships between the objects. It
also identifies the main attributes and operations that characterize each
class.
The process of object
modeling can be visualized in the following steps −
DYNAMIC MODELING
After the static behavior of the system is analyzed, its
behavior with respect to time and external changes needs to be examined. This
is the purpose of dynamic modeling.
Dynamic Modeling can
be defined as “a way of describing how an individual object responds to events,
either internal events triggered by other objects, or external events triggered
by the outside world.”
The process of dynamic
modeling can be visualized in the following steps −
FUNCTIONAL MODELING
Functional Modeling is the final component of object-oriented
analysis. The functional model shows the processes that are performed within an
object and how the data changes, as it moves between methods. It specifies the
meaning of the operations of an object modeling and the actions of a dynamic
modeling. The functional model corresponds to the data flow diagram of
traditional structured analysis.
The process of
functional modeling can be visualized in the following steps −
Object-Oriented
Design
After the analysis
phase, the conceptual model is developed further into an object-oriented model
using object-oriented design (OOD). In OOD, the technology-independent concepts
in the analysis model are mapped onto implementing classes, constraints are
identified, and interfaces are designed, resulting in a model for the solution
domain. The main aim of OO design is to develop the structural architecture of
a system.
The stages for
object–oriented design can be identified as −
OO Design can be
divided into two stages − Conceptual design and Detailed design.
Conceptual design
In this stage, all the
classes are identified that are needed for building the system. Further,
specific responsibilities are assigned to each class. Class diagram is used to
clarify the relationships among classes, and interaction diagram are used to
show the flow of events. It is also known as high-level design.
Detailed design
In this stage,
attributes and operations are assigned to each class based on their interaction
diagram. State machine diagram are developed to describe the further details of
design. It is also known as low-level design.
DESIGN PRINCIPLES
Following are the major design principles −
Principle of
Decoupling
It is difficult to
maintain a system with a set of highly interdependent classes, as modification
in one class may result in cascading updates of other classes. In an OO design,
tight coupling can be eliminated by introducing new classes or inheritance.
Ensuring Cohesion
A cohesive class
performs a set of closely related functions. A lack of cohesion means — a class
performs unrelated functions, although it does not affect the operation of the
whole system. It makes the entire structure of software hard to manage, expand,
maintain, and change.
Open-closed Principle
According to this
principle, a system should be able to extend to meet the new requirements. The
existing implementation and the code of the system should not be modified as a
result of a system expansion. In addition, the following guidelines have to be
followed in the open-closed principle −
- For each concrete class, separate interfaces and
implementations have to be maintained.
- In a multithreaded environment, keep the attributes
private.
- Minimize the use of global variables and class
variables.
Dr. Arpana Chaturvedi
HOD-IT
(BCA)
Department of Information Technology
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