Introduction to Classes Lab

You are going to create a small program that relies on object oriented design. This program is used to demonstrate the object oriented concepts presented in class involving class definitions, attributes and methods, accessor and mutator functions, along with general program structure. The program is designed in three distinct sections:

• The class definition
• The implementation section of source file
• The main() function

Step 1: Launch your compiler, create a new source file and copy in the following code:

//Rectangle Program
//Program designed to demonstrate OO concepts, class definition,
//attributes and methods, accessor and mutator functions, etc.

#include <iostream>
using namespace std;
// Crectangle class
class Crectangle
{
private:
double length; // rectangle’s length
double width; // rectangle’s width

public:
// Default Constructor
Crectangle( );
// Parameterized Constructor
Crectangle (double, double);
// set length & width of existing rect.
void set_dimensions(double, double);
// get length of existing rectangle
double get_length(void);
// get width of existing rectangle
double get_width(void);
// calculate area of existing rectangle
double get_area(void);
};

// IMPLEMENTATION SECTION

// Default Constructor
// Set length and width to 0.0
Crectangle :: Crectangle()
{
length = 0.0;
width = 0.0;
}

// Parameterized Constructor
// Set length and width to passed values
Crectangle::Crectangle(double l, double w)
{
length = l;
width = w;
}
// Assign passed length and width
// to existing object
void Crectangle ::
set_dimensions(double l, double w)
{
length = l;
width = w;
}

// return length of existing object
double Crectangle :: get_length(void)
{
return length;
}
// return width of existing object
double Crectangle :: get_width(void)
{
return width;
}
// calculate and return area of existing
// object based on its data
double Crectangle :: get_area(void)
{
return length * width;
}

// DRIVER PROGRAM

int main( )
{
// Declare local variables for user input
double howWide = 0.0;
double howLong = 0.0;

// Construct kitchen object with
// Default Constructor
Crectangle kitchen;

// Use console I/O to get bedroom dimensions from user
cout << "Enter the length of the bedroom: ";
cin >> howLong;
cout << "Enter the width of the bedroom: ";
cin >> howWide;

// Construct bedroom object with
// Parameterized Constructor
Crectangle bedroom(howLong, howWide);

// Display existing dimensions of
// bedroom object
cout << "The dimensions of the bedroom are ";
cout << bedroom.get_length() << " by ";
cout << bedroom.get_width() << endl;

// Display calc’d area of bedroom obj.
// using dimensions as initialized
cout << "The area of the bedroom is ";
cout << bedroom.get_area() << endl;

// Send kitchen dimensions to its obj.
kitchen.set_dimensions(14.5, 12.0);
// Display dimensions and calculated
// area of kitchen object using
// its data
cout << "The area of the ";
cout << kitchen.get_length() << " by ";
cout << kitchen.get_width();
cout << " kitchen is ";
cout << kitchen.get_area() << endl;

// EOJ
system("pause");
return 0;
}

Step 2: Build, test, and debug

You should see the following when the values 20 and 15 are provided for the bedroom dimensions:

Step 3: Extending Functionality. What if we wanted to strengthen the Crectangle class --- be able to calculate a perimeter . . .

E.G. A fence around the backyard.
E.G. A molding around the kitchen floor.

Questions to consider:
Do we need any new private data members?
Do we need any new public function prototypes?
Do we need to implement anything?
Do we need to change our Test Driver Program?

• In the class definition add the following: (figure out where it goes)
  // calculate perimeter of existing rect
  double get_perimeter(void);
• In the implementation section add the following: (figure out where it goes)

  // calculate and return perimeter of
  // existing object based on its data
  double Crectangle :: get_perimeter(void)
  {
  return (2 * length) + (2 * width);
  }

• In main driver section add the following: (figure out where it goes)
  // Display perimeter of bedroom
  cout << "The perimeter of the bedroom ";
  cout << "is " << bedroom.get_perimeter();
  cout << endl;
  // Display perimeter of kitchen
  cout << "The perimeter of the kitchen ";
  cout << "is " << kitchen.get_perimeter();
  cout << endl;

Step 4: Re-build, Re-test, and Debug

• Recompile your program.
• If no errors, run the program.
• If everything works 'ok', print source code file and do a screen print of the output for turnin.

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