Abstraction-Object Oriented Programming-Lecture Slides, Slides of Object Oriented Programming

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Object-Oriented Programming

(OOP)Lecture No. 3

Abstraction

►Abstraction is a way to cope withcomplexity. ►Principle of abstraction:“Capture only those details about an objectthat are relevant to current perspective”

Example – Abstraction ►Attributes- Name^

• Employee ID
  • Student Roll No
  • Designation
    • Year of Study
    • Salary
      • CGPA^
      • Age

Ali is a PhD student and teaches BSstudents

Example – Abstraction Ali is a PhD student and teaches BSstudents ►behaviour- Study^

• DevelopExam
  • GiveExam^
  • TakeExam
    • PlaySports^
    • Eat
      • DeliverLecture
      • Walk

Example – Abstraction ►Attributes- Name^

• Employee ID
  • Student Roll No
  • Designation
    • Year of Study
    • Salary
      • CGPA^
      • Age

Student’s Perspective

Example – Abstraction^ Student’s Perspective ►behaviour- Study^

• DevelopExam
  • GiveExam^
  • TakeExam
    • PlaySports^
    • Eat
      • DeliverLecture
      • Walk

Example – Abstraction ►Attributes- Name^

• Employee ID
  • Student Roll No
  • Designation
    • Year of Study
    • Salary
      • CGPA^
      • Age

Teacher’s Perspective

Example – Abstraction^ Teacher’s Perspective ►behaviour- Study^

• DevelopExam
  • GiveExam^
  • TakeExam
    • PlaySports^
    • Eat
      • DeliverLecture
      • Walk

Example – Abstraction ►Ordinary PerspectiveA pet animal with  Four Legs  A Tail  Two Ears  Sharp Teeth

►Surgeon’s PerspectiveA being with^ ^ A Skeleton^ ^ Heart^ ^ Kidney^ ^ Stomach

A cat can be viewed with differentperspectives

Example – Abstraction Driver’s View

Engineer’s View

Abstraction – Advantages ►Simplifies the model by hiding irrelevantdetails ►Abstraction provides the freedom to deferimplementation decisions by avoidingcommitment to details

Classes

►In an OO model, some of the objects exhibitidentical characteristics (informationstructure and behaviour) ►We say that they belong to the same class

Example – Class

►Ali studies mathematics ►Anam studies physics ►Sohail studies chemistry ►Each one is a Student ►We say these objects are

instances of the

Student class

Example – Class

►Ahsan teaches mathematics ►Aamir teaches computer science ►Atif teaches physics ►Each one is a teacher ►We say these objects are

instances of the

Teacher class

Graphical Representation of Classes^ (Class Name)(attributes)(operations)

(Class Name)

Normal Form

SuppressedForm

Example – Graphical Representation

of Classes Circle

centerradiusdrawcomputeAreaNormal Form

CircleSuppressedForm

Example – Graphical Representation

of Classes Person nameagegendereatwalk

Normal Form

Person SuppressedForm

Inheritance

►A child inherits characteristics of its parents ►Besides inherited characteristics, a childmay have its own unique characteristics

Inheritance in Classes ►If a class B inherits from class A then itcontains all the characteristics (informationstructure and behaviour) of class A ►The parent class is called

base class and the

child class is called

derived class

►Besides inherited characteristics, derivedclass may have its own uniquecharacteristics

Example – Inheritance^ Person Teacher

Doctor

Student

Example – Inheritance^ Shape

Circle

Triangle

Line

Inheritance – “IS A” or“IS A KIND OF” Relationship ►Each derived class is a special kind of itsbase class

Example – “IS A” Relationship

Person nameagegendereatwalk Teacherdesignationsalaryteach StudentprogramstudyYearstudy

DoctordesignationsalarycheckUp

Example – “IS A” Relationship

Shape colorcoorddrawrotatesetColor Circleradiusdraw

Linelength

Triangleangledraw

Inheritance – Advantages ►Reuse ►Less redundancy ►Increased maintainability