This is such a big problem. Essentially there is no difference, it is just C++ class inheritance. However, ATL's template design was so exquisite that the later C++ standard library also learned from it.
I have only read books about COM and have not practiced it. After all, there are very few opportunities to use it now. If someone tells you a detailed answer, you may be able to fully understand it. You are still familiar with the principles of COM. If you read the ATL book, you should understand it.
This is such a big problem. Essentially there is no difference, it is just C++ class inheritance. However, ATL's template design was so exquisite that the later C++ standard library also learned from it.
I have only read books about COM and have not practiced it. After all, there are very few opportunities to use it now. If someone tells you a detailed answer, you may be able to fully understand it. You are still familiar with the principles of COM. If you read the ATL book, you should understand it.