COM Registration

The system registry holds the information so that COM can start the right server when a client wishes to create a COM object. The registry can be accessed by a human user using regedit, or by a Carapace script using the Registry class.

COM also needs to know what COM objects can be create by a COM server and what each of these objects can do. This information is held in type libraries -- a type library can be viewed using oleview. Also, Carapace can create a type library using the TypeLibrary class. A type library uses the .tlb extension when held as a file on disk.

COM has a special part at the top level of the system registry to hold its registration information. This is at HKEY_CLASSES_ROOT -- quite an intimidating amount and complexity of information, made worse by the heavy use of GUIDs which are pretty impenetrable to us humans.

If you want to have a look at this information just be careful you don't delete or alter anything inadvertently! Some major sections in this HKEY_CLASSES_ROOT hive are as follows:

• CLSID - holds a list of all registered COM classes
• Interface - holds a list of all registered COM interfaces
• TypeLib - holds a list of type libraries

All the above sections contain hundreds of subsections having a GUID as their name.

Most other top-level information in the HKEY_CLASSES_ROOT hive consists of sections describing registered COM objects -- our Trumpet example object will be there as

    Carapace.Trumpet