Either this macro or IMPLEMENT_OLECREATE_FLAGS must appear in the implementation file for any class that uses DECLARE_OLECREATE.
If you use IMPLEMENT_OLECREATE, by default, you support only the single threading model. If you use IMPLEMENT_OLECREATE_FLAGS, you can specify which threading model your object supports by using the nFlags parameter.
The external name is the identifier exposed to other applications. Client applications use the external name to request an object of this class from an automation server.
The OLE class ID is a unique 128-bit identifier for the object. It consists of one long, two WORDs, and eight BYTEs, as represented by l, w1, w2, and b1 through b8 in the syntax description. The Application Wizard and code wizards create unique OLE class IDs for you as required.