Marks the beginning of the category map.
The category map is used to specify which component categories the COM class will implement and which categories it requires from its container.
Add an IMPLEMENTED_CATEGORY entry to the map for each category implemented by the COM class. Add a REQUIRED_CATEGORY entry to the map for each category that the class requires its clients to implement. Mark the end of the map with the END_CATEGORY_MAP macro.
ATL uses the standard component categories manager to register component categories. If the manager is not present on the system when the module is registered, registration succeeds, but the component categories will not be registered for that class.
For more information about component categories, see What are Component Categories and how do they work? in the Windows SDK.