CS-3333R Object Oriented Technology

Object Oriented Programming in C++

Lafore, Robert

Chapter 1 The Big Picture

Why Do We Need Object-Oriented Programming
   Procedural Languages
      C, Pascal, COBOL, these are all procedural languages
      In procedural languages each line tells computer to do something
      Works well for small programs
      Division into functions
         As programs become larger they become harder to understand
         Functions were developed
         Grouping functions together in a separate entity is called a module
      Problems with Structured Programming
         Large Programs become complex
         Functions have unrestricted access to global data
         Unrelated functions and data provide poor models of the real world
      Unrestricted Access
         Two types of data
            Local
               inside functions
               used only by those functions
            Global
               Accessed by any function
               Leads to potential connections between functions and data
                  Difficult to conceptualize
                  Difficult to modify
            Real World Modeling
               Attributes - (characteristics)
                  Equivalent to data in person (blue eyes)
                  have a specific value
               Behaviour
                  How some things respond to stimulus
                  Like a function, it does what it is told to do.
   The Object-Oriented Approach
      Create a unit that contains data and functions to manipulate data
         Only way to access data is through object functions
         Data that does not need to be changed is hidden
      An Analogy
         Think of objects as departments in company
         Each department controls its own data
         One department gets data from another department by going through proper channels
      OOP: An Approach to Organization
         C+ statements look the same as procedural language statements and Object-Oriented Programming statements
         Only when they are viewed in context can one tell which they are
Characteristics of Object-Oriented Languages
   Objects
   Classes
      a description of a number of similar objects
      An object is called and instance of a class
   Inheritance
      In natural life we group things together because they are similar
      A bus and a car do not look the same but they are both vehicles, maybe cause one characteristics is wheels
      In OOP we have a base class that we reuse and they are called derived classes.
      Derived classes inherit their information the base class and add some of their own..(bus has lots of seats, car has limited amount, but vehicles has wheels and seats)
   Reusability
   Creating New Data Types
      We can create types to match what we need to do
      We can send the information to the class that we create
   Polymorphism and Overloading
      We can define what normal operators do while in the the class (overloading)
      We can use functions and operators in different ways (Polymorphism)
C++ and C
   Is a subset of C
   Originally called C with classes
Laying the Groundwork
The Unified Modeling Language (UML)
   UML provides way to visualize higher-level organization of programs
   Programmer does not have to get caught up in details of actual code.
   Important part of UML is diagrams
      Class diagrams about how the classes relate
      Sequence diagrams show how classes communicate
Summary
Questions

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