The “body” class

class body {

public:

virtual float GetVolume() =0;

virtual float GetSurface() =0;

};

virtual float GetVolume() =0;

Meaning

this function can be overridden by a more specific one in a subclass

function returns a float value

this virtual function must in fact be overridden; the class “body” cannot be instantiated, only a specific sub-class.