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### Circle Class Problem

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:
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
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.
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.
LOL I have no clue that is just the way the question is worded!
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)
double Area();

private:
// member variables (data)
};

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;

circleArea = myCircle.Area();

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

return 0;
}// end of main

// class implementation

// default constructor
Circle::Circle()
{
}

// copy constructor
Circle::Circle(const Circle & Object)
{
}

// sets the radius of the circle
{