SPHERE.H

The default argument passing method in C++, pass-by-value, creates a copy of the passing argument.
Passing arguments can be expensive and problematic when passing abstract data types such as class objects.
Function arguments can be passed by constant reference using a combination of the & and const directives.

class sphere 
	{
	public:
	sphere(void);
	~sphere(void);
	void copy(const sphere&);
	void setRadius(float);
	float getRadius(void);
	protected:
	float xPosition;
	float yPosition;
	float zPosition;
	private:
	void resetPosition(void);
	float diameter;
	};

SPHERE.CXX

Without a const reference the calling function can change the argument and may lead to side affects.

#include "sphere.h"

sphere::sphere(void)
	{
	resetPosition();
	diameter = 0.0;
	}	

sphere::~sphere(void)
	{
	}	

void sphere::copy(const sphere& fromSphere)
	{
	xPosition = fromSphere.xPosition;
	yPosition = fromSphere.yPosition;
	zPosition = fromSphere.zPosition;
	diameter = fromSphere.diameter;
	}

void sphere::setRadius(float value)
	{
	diameter = value*2.0;
	}

float sphere::getRadius(void)
	{
	return diameter/2.0;
	}

void sphere::resetPosition(void)
	{
	xPosition = 0.0;
	yPosition = 0.0;
	zPosition = 0.0;
	}