An operating system that provides a graphical interface for PDAs and consumer-oriented devices from the Breadbox Computer Company, Brooksville, FL (www.breadbox.com). Originally developed by Geoworks Corporation of Emeryville, CA, the GEOS patents were licensed and then sold to Breadbox in 2003.

GEOS was the underlying OS in Geoworks Ensemble and ran on top of DOS. Originally available on the Commodore 64 and Apple II, PC GEOS was introduced in 1990. GEOS SC was a later 32-bit object-oriented version used for cellphones. See Geoworks Ensemble.