Introduction to Object Oriented Programming OOP

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IntroductiontoObject OrientedProgramming (OOP)
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Introduction

• Many programming approaches have been tried to
  handle complex problems

• modular programming

• top-down programming

• bottom-up programming

• structured programming

• Object Oriented Programming (OOP)

• latest programming approach to handles
  problems

• Eliminate some of the pitfalls of conventional
  programming

• Model real-world problems well

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Procedure-Oriented Programming

• Use high level languages such as Pascal, C.

• Problem is viewed as a sequence of things to
  be done

• reading

• calculating

• printing, etc.

• Functions are written to accomplish this task.

• Primary focus on functions.

• Very little attention to data that are being
  used by various functions

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Structure of procedure-oriented programs
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Procedure-Oriented (Cont.)

• Drawbacks

• Global data more prone to unintentional change

• In large programs, difficult to identify what
  data is used by which functions.

• In case of revising an external data
  structure, need to revise all functions that
  access the data

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Procedure-Oriented (Cont.)

• Some characteristics

• Emphasis is on doing things (algorithms).

• Large programs are divided into smaller
  programs known as functions.

• Most of the functions share global data.

• Data move openly around the system from
  function to function.

• Functions transform data from one form to
  another.

• Employs top-down approach in program design.

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OOP Paradigm

• OOP

• treats data as critical factor in the program
  development

• does not allow data to flow freely around the
  system

• ties data to functions that operate on it

• protect data from accidental changes from
  outside functions

• Decompose a problem into a number of entities
  called objects (datafunctions).

• Data of an object can be accessed only
  functions that bind to the object

• However, functions of one object can access
  the functions of other object.

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Organization of data and functions in OOP
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Object-Oriented (Cont.)

• Some of the important features

• Emphasis is on data rather than procedure.

• Programs are divided into what are known as
  objects.

• Data structures are designed such that they
  characterize the 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.

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Basic Concepts of OOP

• Objects

• Basic run-time entities

• May be a person, a place, or any item

• Problem analyzed in terms of objects and nature
  of communication between them

• Objects should be chosen s.t. they match
  closely with real-world object.

• Objects interact by sending messages to one
  another.

• Customer object sends a message to Account
  Object requesting current balance.

• They can interact without knowing each others
  data and codes.

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Representation of an object
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Basic Concepts of OOP (Cont.)

• Classes

• Collection of similar objects

• Once a class has been defined, we can create
  any number of objects belonging to that class.

• mango, apple and orange are objects of the
  class Fruit.

• Classes are user-defined data types and behave
  like built-in data types.

• Fruit mango

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Basic Concepts of OOP (Cont.)

• Data Abstraction and Encapsulation

• Encapsulation - combing of the data and
  functions into a single unit (called class)

• Data hiding data is not accessible to the
  outside world (other classes)

• Data abstraction includes only features
  relevant to the problem neglecting other
  unnecessary details

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Basic Concepts of OOP (Cont.)

• Inheritance

• Process by which objects of one class acquire
  the properties of objects of another class.

• Reusability that we can add additional
  features to an existing class without modifying
  it

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Basic Concepts of OOP (Cont.)

• Polymorphism

• Ability to take more than one form.

• The behavior depends on the types of data used
  in operation.

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Benefits of OOP

• Through inheritance, we can eliminate
  redundant code and extend the use of existing
  classes.

• We can build programs from standard working
  modules rather than having to start from the
  scratch. This leads to saving of development
  time higher productivity.

• Data hiding helps the programmer to secure
  programs that cannot be invaded by code in
  other parts of the program.

• It is possible to map objects in the problem
  domain to those objects in the program.

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Benefits of OOP (Cont.)

• It is easy to partition the work in a project
  based on objects.

• The data-centered 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.