It evolved like this

when u write a CLASS to reuse in a application, multiple

intances of the class exists with each instance of

application,

Next u want to avoid it so u make a class and put it in DLL

now only one instance exists though multiple instances of

applications exists

Applicatoin needs to be recompiled whenever Dll is

modified, SO came COM.

COM is independent component that internally handles

networking, resources etc, COM uses IDL to communicate to

different languages