I am having trouble understanding classes and this is the first problem I have to do. If I could get some help with it I will be able to do the rest of my homework.

Write a Circle class that has the following member variables:

radius: a double

pi: a double initialized with the value 3.14159

The class should have the following member functions:

Default Constructor. A default constructor that sets the radius to 0.0

Constructor. Accepts the radius of the circle as an argument

setRadius. A mutator function for the radius variable

getRadius. An accessor function for the radius variable

getArea. Returns the area of the circle, which is calculated as diameter=pi*radius*radius

getDiameter. Returns the diameter of the circle, which is calculated as diameter=radius*2

getCircumference. Returns the circumference of the circle, which is calculated as circumference=2*pi*radius

Write a program that demonstrates the Circle class by asking the user for the circle's radius, creating a circle object, and then reporting the circle's area, diameter, and circumference.

Write a Circle class that has the following member variables:

radius: a double

pi: a double initialized with the value 3.14159

The class should have the following member functions:

Default Constructor. A default constructor that sets the radius to 0.0

Constructor. Accepts the radius of the circle as an argument

setRadius. A mutator function for the radius variable

getRadius. An accessor function for the radius variable

getArea. Returns the area of the circle, which is calculated as diameter=pi*radius*radius

getDiameter. Returns the diameter of the circle, which is calculated as diameter=radius*2

getCircumference. Returns the circumference of the circle, which is calculated as circumference=2*pi*radius

Write a program that demonstrates the Circle class by asking the user for the circle's radius, creating a circle object, and then reporting the circle's area, diameter, and circumference.

I suggest you read over this carefully. It goes over everything you listed.

http://www.cplusplus.com/doc/tutorial/classes/

If you have started to write the code and are still stuck, feel free to post what you have and we can help from there.

http://www.cplusplus.com/doc/tutorial/classes/

If you have started to write the code and are still stuck, feel free to post what you have and we can help from there.

Why would pi be a member variable? For one thing, it is a constant. For another, each individual circle doesn't need its own separate value of pi.

But still, that doesn't help you. I'm just puzzled by the design.

But still, that doesn't help you. I'm just puzzled by the design.

This is what I have so far. All the program does is ask for radius then closes

#include <cstdlib>

#include <iostream>

using namespace std;

#include <iostream.h>

#include <math.h>

const double PI = 3.14159;

// class interface (definition)

class Circle

{

public:

// constructors

Circle(); // default constructor

Circle(const Circle &); // copy constructor

// member functions (methods)

void SetRadius(double); // modifier that sets new radius

double Area();

private:

// member variables (data)

double radius; // circle's radius

};

int main()

{

Circle myCircle; // circle object used as an example

double circleArea = 0.0; // area of the circle

double userInput = 0.0; // user input for radius of circle

cout << "Enter radius of the circle: ";

cin >> userInput;

myCircle.SetRadius(userInput);

circleArea = myCircle.Area();

cout << "The area is " << circleArea << endl << endl;

return 0;

}// end of main

// class implementation

// default constructor

Circle::Circle()

{

radius = 0.0;

}

// copy constructor

Circle::Circle(const Circle & Object)

{

radius = Object.radius;

}

// sets the radius of the circle

void Circle::SetRadius(double IncomingRadius)

{

radius = IncomingRadius;

}

// computes the area of the circle

double Circle::Area()

{

return(PI * pow(radius, 2));

}

#include <cstdlib>

#include <iostream>

using namespace std;

#include <iostream.h>

#include <math.h>

const double PI = 3.14159;

// class interface (definition)

class Circle

{

public:

// constructors

Circle(); // default constructor

Circle(const Circle &); // copy constructor

// member functions (methods)

void SetRadius(double); // modifier that sets new radius

double Area();

private:

// member variables (data)

double radius; // circle's radius

};

int main()

{

Circle myCircle; // circle object used as an example

double circleArea = 0.0; // area of the circle

double userInput = 0.0; // user input for radius of circle

cout << "Enter radius of the circle: ";

cin >> userInput;

myCircle.SetRadius(userInput);

circleArea = myCircle.Area();

cout << "The area is " << circleArea << endl << endl;

return 0;

}// end of main

// class implementation

// default constructor

Circle::Circle()

{

radius = 0.0;

}

// copy constructor

Circle::Circle(const Circle & Object)

{

radius = Object.radius;

}

// sets the radius of the circle

void Circle::SetRadius(double IncomingRadius)

{

radius = IncomingRadius;

}

// computes the area of the circle

double Circle::Area()

{

return(PI * pow(radius, 2));

}

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