GEOS

from The Free On-line Dictionary of Computing (8 July 2008)

GEOS

   A small windowing, {microkernel} (less than 64 kbytes long)
   operating system written in heavily {bum}med {assembly
   language} for {MS-DOS} computers.  It {multitasks} rather
   nicely on a 6 Mhz {Intel 80286} with at least 512K memory.

   It was adapted to {PDAs} by adding pen recognition, which
   doesn't work very well.

   Usenet newsgroup: news:comp.os.geos.

   (1995-01-21)