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What is COM?

101 100+
What exactly is the Component Object Model in regards to compilers and code? I know the textbook definition, but I'm not sure what it actually does and how it works. Is it a library of classes, or a windows service... or something else entirely?

How exactly does COM interact with OLE, OLE Automation, ActiveX, and COM+? When I open up a .ocx file in notepad, it just gave me garbage, so I'm guessing it's already compiled and works like a dll. If so, what are the differences and how does it communicate between languages?

What I want is to start being able to program activeX controls and dlls for a program that uses them, but it's not enough for me to just know how to code it (although, that would help too). I'd like to understand the big picture.

I know what COM does and what it's for, but not what it physically is on the computer.

Thanks for any help on the issue
Jun 9 '07 #1
3 3133
drhowarddrfine
7,435 Expert 4TB
It's been a long time since I've messed with it. Believe it or not, I did it with assembly language. iirc, it's original purpose was to allow programmers to to swap out old code for new without affecting anything. COM is a pointer to a pointer so you only had to swap out what the second pointer pointed to and that could update your software. How that ties in to DLLs and ActiveX, I don't remember. I don't do Windows anymore.
Jun 9 '07 #2
zensunni
101 100+
Thanks for the response. I've also been able to find these links, which have proven very helpful:

http://www.codeproject.com/com/comintro.asp
http://qtnode.net/wiki/Open_Source_Activex

Now, all I need is a definitive list of windows COM objects so that I can play with windows components... anyone know where to find that?

Of course, I'll post if I find something.
Jun 9 '07 #3
drhowarddrfine
7,435 Expert 4TB
That's not hard. Look at MSDN here and here.
Jun 10 '07 #4

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