Source : Free On-Line Dictionary of Computing

GEOS
     
        A small windowing, {microkernel} (less than 64 kbytes long)
        operating system written in heavily {bum}med {assembly
        language} for {MS-DOS} computers.  It {multitask}s rather
        nicely on a 6 Mhz {Intel 80286} with at least 512K memory.
     
        It was adapted to {PDA}s by adding pen recognition, which
        doesn't work very well.
     
        {Usenet} newsgroup: {news:comp.os.geos}.
     
        (1995-01-21)