Method 1.   #include "objbase.h"  //~~~!! for interface identifier  #include "stdio.h"   interface IAnimal  {      virtual void Forward() = 0;      virtual void Eat() = 0;  };   class CBird : public IAnimal  {    virtual  void Forward()      {          printf( "walk 3 steps \n" );      };     virtual  void Eat()      {          printf( "eat 5 rice \n" );      };  };   void main()  {        IAnimal *pAnm = NULL;      CBird bird;          pAnm = &bird;      pAnm->Forward();    }   In this method, you need to #include "objbase.h" . And write pure virtual func. in the interface class.   Method 2.  In VS7 Microsoft has judged __interface introduction in c++ compiler( macOS c++  support?...)  In the msdn   __interfa...