Uh...I don't mean any disrespect, Jeff, but technically speaking, the Zoomer is a DOS computer. DataLight's ROM-DOS is included in the ROM of the Zoomer and it runs before GEOS loads.
There are the two hidden bootstrap files that you'd expect with any DOS, and a COMMAND.COM. When you reset the Zoomer, it runs through a CONFIG.SYS and AUTOEXEC.BAT file, just like any DOS computer. The last thing in the AUTOEXEC.BAT is a command to start up GEOS, which runs on top of DOS, and uses standard DOS file structures.
Now.. it's difficult, but not impossible, to get to the DOS prompt on the Zoomer. Running DOS programs on the Zoomer is not supported by the manufacturers and doesn't make much sense. For example, consider that if you did find your way outside of GEOS to the DOS prompt somehow, you'd have no input mechanism at all, since the pen input and handwriting recognition are both functions of GEOS-based drivers and libraries.
However, technically speaking, every file on the Zoomer is a DOS file. Some of them are also GEOS files, which just means they have a special file header (the first portion of the file) which contains codes that helps GEOS to recognize which application created the file and what kind of a GEOS file it is. Other files, like text files saved from within the AOL application, or like the autoexec.bat file for example, are just plain DOS files, same as on your desktop computer.
One of the nice things about the Zoomer, in comparison to some other similar products on the market, is the fact that all the files conform to standard DOS conventions, so when dealing with file transfer and connectivity, we're all treading on familiar ground.