C++ Class Member Function default arguments

#include  <iostream.h>
#include  <math.h>
const float PI = 3.14159;  // Approximate value of pi.
// A sphere class.
class Sphere//from  w  ww  . j  a v  a 2  s  .com
{
   public:
   float r;        // Radius of sphere
   float x, y, z;  // Coordinates of sphere
   Sphere(float xcoord, float ycoord = 2.0, float zcoord = 2.5, float radius = 1.0)
   {
      x = xcoord;
      y = ycoord;
      z = zcoord;
      r = radius;
   }
   ~Sphere()
   {
      cout << "Sphere (" << x << ", " << y << ", " << z << ", " << r << ") destroyed\n";
   }
   inline float volume()
   {
      return (r * r * r * 4 * PI / 3);
   }
   float surface_area()
   {
      return (r * r * 4 * PI);
   }
};
void main()
{
   Sphere s(1.0);                // use all default
   Sphere t(1.0, 1.1);           // override y coord
   Sphere u(1.0, 1.1, 1.2);      // override y and z
   Sphere v(1.0, 1.1, 1.2, 1.3); // override all defaults
   cout << "s: X = " << s.x << ", Y = " << s.y << ", Z = " << s.z << ", R = " << s.r << "\n";
   cout << "The volume of s is " << s.volume() << "\n";
   cout << "The surface area of s is " << s.surface_area() << "\n";
   cout << "t: X = " << t.x << ", Y = " << t.y << ", Z = " << t.z << ", R = " << t.r << "\n";
   cout << "The volume of t is " << t.volume() << "\n";
   cout << "The surface area of t is " << t.surface_area() << "\n";
   cout << "u: X = " << u.x << ", Y = " << u.y << ", Z = " << u.z << ", R = " << u.r << "\n";
   cout << "The volume of u is " << u.volume() << "\n";
   cout << "The surface area of u is " << u.surface_area() << "\n";
   cout << "v: X = " << v.x << ", Y = " << v.y << ", Z = " << v.z << ", R = " << v.r << "\n";
   cout << "The volume of v is " << v.volume() << "\n";
   cout << "The surface area of v is " << v.surface_area() << "\n";
   return;
}