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...