After a mis-step or two (I told you I didn't get along well with Macs) it is up and running.

When I plugged the flash drive into the iMac, I clicked on the zip file while it was on the flash drive instead of copying the zip file to the desktop. Then I ran the app from the flash drive. Not the right way to do it. I copied the app to the "Applications" directory, but could not figure out how to make the app running from the flash drive stop running so I could re-start it from the copy in the Applications directory. Finally out of frustration I just pulled the flash drive out of the USB port, amidst dire warnings about damage to file structure, eject it first next time, iMac will try and repair damage, and for all I know global warming and world-wide economic collapse, and restarted the app from the Applications Directory instead of the flash drive, and was pleased to find that it did not overwrite the output file but continued on, appending to it. Nice touch, that.

Thank you for the help.

tanstaafl.