Object Oriented Programming

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Object Oriented Programming

• 03/24/2005

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Need for OOP

• Complexity
• MS Word is 500,000 lines of code
• 50 lines per page
• 10,000 pages
• 40 paperbacks

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Need for OOP

• Code Reuse
• Good programmer can generate 100 lines per day
• 5000 days (13.7 years)
• Code Sharing
• Team programming
• Less coordination needed
• Divide the book into chapters

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Need for OOP

• GUI
• Event driven
• Software is waiting for user input

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OOP

• Higher level of abstraction
• Views the world as a collection of Objects
• Object is a grouping of some data together with
  the instructions that act on the data.
• Self-contained bundle
• Object is a meaningful thing

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OOP

• About simulating or modeling real-word problems
• Model is built from objects that interact
• The closer the model is to reality the better the
  program will do what is desired.

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OOP

• Examples
• Word processor
• Words, pages, lines, headings
• Airline reservation system
• Flights, seats , destinations
• Student information system
• Students, classes, majors

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Objects

• Tools that provide the programmer with two
  things
• Modularity
• a program consists of separate self-contained
  objects
• Simulation
• A powerful idea for modeling real-word problems

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Classes

• General type of object
• Abstract model
• Programmer creates specific instances of the
  class
• Vehicle (class)
• Car
• Truck
• SUV

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OOP Programming

• Describes the nature of the various classes that
  the program will use
• Create the necessary objects
• Write instructions on how the objects interact

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Inheritance

• Classification scheme
• Classes can pass on their traits
• New class
• Old class (superclass, ancestor)
• New stuff (subclass, descendent)

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Properties

• Objects have traits
• Student
• Student ID, Name, DoB, Major, Grades
• Data to be used in the program
• Variables

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Methods

• Procedures for manipulating the objects
• Add new grade to student
• Name change
• Only way traits can be accessed and manipulated
• Encapsulation

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What Have We Gained?

• Code reuse
• No re-inventing the wheel
• Improvement in reliability
• Better maintainability
• A more natural word-view
• Escape from procedural scripts
• Reality is not sequential