(to Melissa)
I can`t understand how COM & C++ related.
COM technology present in early 16 bit windows in times when C++ just not existed.
C++ supported COM, but COM never was part of C++.
I could say COM is specification for MS vtable in assembly (because it is independent from compiler).

COM is language independent because it is spec that you can implement. But C++ part is
that they implemented in C++ compiler

reason and effect are ...
I can implement COM in assembly because COM is language independent. But not in reverse order.
COM implementation is part of C/C++/C#/pascal/basic. (In basic it was based only over IDispatch)
If someone would digging deeper than COM implementation would be in assembly too (partialy already exists).

In C++, you don't even have to use virtual functions. You can just implement it like in C, manually, with a pointer to a struct of function pointers (the "vtable"). Same with asm.