What is COM?

Question

I searched hard, but was unable to grasp the whole idea. Can anyone tell me:

• What COM actually is?
• How do GUIDs work, and how are they used by COM? <

Answer 1

Your question is a little large for a full explanation here. A quick high-level introduction to COM can be found in the book Understanding ActiveX and OLE. A more detailed but still introductory introduction is Inside COM. The best book on the subject is Don Box's Essential COM.

A couple of quick answers:

• COM is a binary interface standard for objects. It allows various programs to write to interfaces without all having to have been written in the same langauge with the same compiler. There are also related services available.
• GUIDs are globally unique numbers that COM uses to identify interfaces.
• COM doesn't resolve different DLL version problems. It only allows a single DLL to be registered for each GUID.