A class in a namespace

#include <iostream>
using namespace std;

const double PI = 3.14159;

namespace FlatShapes
{
    class Circle
    {
    public:
        void setRadius(const double r);
        double getRadius() const;
        double Diameter() const;
        double Circumference() const;
        double Area() const;
    private:
        double Radius;
    };

	class Square
	{
	private:
		double Side;
	public:
		void setSide(const double s) { Side = s; }
		double getSide() const { return Side; }
		double Perimeter() const { return Side * 4; }
		double Area() const { return Side * Side; }
	};
}

namespace FlatShapes
{
	void FlatShapes::Circle::setRadius(const double r)
	{
		Radius = r; 
	}

	double FlatShapes::Circle::getRadius() const
	{
		return Radius;
	}

	double FlatShapes::Circle::Diameter() const
	{
		return 2 * Radius; 
	}

	double FlatShapes::Circle::Circumference() const
	{
		return 2 * Radius * PI; 
	}

	double FlatShapes::Circle::Area() const
	{
		return Radius * Radius * PI;
	}
}

int main()
{
    FlatShapes::Circle Round;
	
	Round.setRadius(20.62);

    cout << "Characteristics of the circle";
    cout << "\nRadius: " << Round.getRadius();
    cout << "\nDiameter: " << Round.Diameter();
    cout << "\nCircumference: " << Round.Circumference();
    cout << "\nTotal Area: " << Round.Area();    
    
	FlatShapes::Square Sous;

	Sous.setSide(42.28);
	cout << "\n\nSquare Area: " << Sous.Area();

	cout << "\n\n";
    return 0;
}