程序代码：

namespace Geometry_computation
{
    class circle //圆类
    {
        public const double PI = 3.14159265;
        private double r;
        public circle(double a) { r = a; }
        public void area()
        {
            Console.WriteLine("圆的面积为:{0}", r * r * PI);
        }
        public void circumference
        {
            Console.WriteLine("圆的周长为:{0}",2*r*PI);//这里显示的是：应为get或者set访问器
        }
    };
    class globe:circle//球类
    {
      
    };
    class Program
    {
        static void Main(string[] args)
        {
        }
    }
}