Twain.dll

I have two devices, a flatbed scanner and a web cam that use the twain interface. I now want to add twain capability to my Olympus digital camera. In searching for the twain driver for the camera I began to ask myself a question that I couldn't answer about dlls and in particular the twain.dll.

When I install a twain driver for another device, such as the camera, what happens to the twain.dll file on my system.
a) Does the new device overwrite the original, in which case how does it retain the information on the any previously installed devices?
b) Does it modify the dll in some way?
c) Is there just a registry change that points the new device to the twain.dll?

Perhaps someone can lighten my darkness.

Thanks

The twain.dll for all are most likely the same and are shared. If one is newer it may update the old and is still used (as a shared file) by the other devices.

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