D = C + IDL instead of .h for interface (allows C++ smartpointers and C usage)

**** .idl ****

interface IXxxx : IUnknown

library XxxxLibrary
    coclass CoXxxx

**** .h ****

class CoXxxx : ITest
// IUnknown methods
// IXxxx methods

class CoXxxxFactory : IClassFactory
// IUnknown methods
// IClassFactory methods

**** registry ****

name -> co class GUID
co class GUID -> name
co class GUID -> DLL
co class GUID -> library GUID
library GUID -> library

**** C++ usage ****

IClassFactory *f = CoGetClassObject()
IXxxx o = f->CreateInstance()

or:

IXxxx o = CoCreateInstance()

or:

import tlb

IXxxxPtr p
IXxxxPtr.CreateInstance()

or:

IXxxxPtr p()

**** C usage ****

IXxxx o = CoCreateInstance()
IXxxx_Something(o, ...)

**** actions ****

translate CLSID to DLL via registry
load DLL
call DllGetClassObject to get instance of factory
call factory CreateInstance with IID to get instance (calls AddRef on instance)

use instance

call Release