I think I see where the confusion is coming from here. The comport.txt file is an advanced way of getting input from a serial port--it is typically used when lots of continuous data are coming in--as opposed to single button presses. We CAN use this method for your Cedrus box, but let's see if we can do it with TTL first.

The IOTest program is for setting up and testing the simpler TTL functionality--which is used most often for single button presses. For that, you do need an address, and I'm guessing that Windows assigns one to the pretend com port that it creates via the USB driver. Try this:

Go to the Windows Device Manager and head to the COM3 listing for the Cedrus device. Double click that and then click on the resources tab. What do you see? You should see the address that has been assigned to the simulated port. It will be a hexidecimal value.

And in answer to your question regarding 888 and 889, that is because different addresses are assigned to the parallel port--888 is for output and 889 is for input. That is why you often see a range of values in the "resources" tab for a port. Some will be for input and some for output. Although 888 and 889 aren't used for every machine, the input and output addresses will often be sequential like that.

-Blair