Lab Session-2 CSIT221 Spring 2003

1
Lab Session-2 CSIT221 Spring 2003

• Intro to Object Oriented Programming
• Practice Problem
• Lab Exercise (Demo Required)

2
Object Oriented Programming

• We start our lab today with an introductory
  session for object oriented programming
• OOP involves following steps
• Definition of class in a header file including
  prototypes of member functions and private data
• Implementation of public member functions
• Testing with a driver program

3
Practice Problem

• Define a class cat that includes private data
  members weight and color of the cat and some
  public member functions
• Write a driver program that tests out the class
  by defining two objects that belong to this class

4
Building Class Definition

• The class definition will consist of public and
  private sections. By default, everything is
  private. However, we should explicitly label the
  sections as such to avoid confusion
• The function prototypes and the data items are
  included in the definition of a class. However,
  data items cannot be initialized here.
  Initialization takes place in a constructor

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Constructor

• Once the class definition is completed, Start
  building up the source code for all the member
  functions in the implementation file
• The first one to be written is the constructor.
  The default constructor accepts no arguments and
  executes by default when an object of this class
  is declared

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How Many Files?

• Class definition in a header file (e.g. cat.h)
• Class implementation in a C source code file
  (e.g. cat_imp.cpp)
• Class driver code in a C source code file (e.g.
  cat_test.cpp)
• All these files are part of your project

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Be Careful

• Use the keyword void in the implementation file
  before starting to implement any void member
  function
• If parameters are being passed to a member
  function, specify their data types and local
  names
• The order of inserting files may influence the
  number of compiling errors

8
Lab Exercise (Demo required on 2/11 for Sec-1 and
2/13 for Sec-2)

• Model a vending machine as an object. Develop a
  class definition for a vending machine that has
  an initial quantity of ten bottles each for 5
  different soft drinks and 95 cents change and
  zero dollars in bills. As the users operate the
  machine, they insert one dollar bills and/or
  coins to buy the soft drinks. The machine can
  display and change the number of bottles of each
  type and its total cash with the help of member
  functions. The driver program cannot alter any
  private data. All private data must be handled by
  the member functions only. Show a complete demo
  with the following scenario

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User Scenario

• Display total number of all types of soft drinks
  and cash at hand
• Let the user buy two bottles
• Display the balance cash and bottles
• Let the user buy three bottles
• Display the balance cash and bottles
• Let the vendor take away the cash and fill up the
  machine
• Display the balance cash and bottles