Source : Free On-Line Dictionary of Computing

Xerox Data Systems Model 940
     
         (SDS 940, XDS 940) A {time-sharing} system,
        announced in February 1966, developed by {Scientific Data
        Systems} with help from The {University of California at
        Berkeley} and {Tymshare}.  SDS 940 was {backward compatible}
        with SDS's previous systems (except the 12-bit {SDS 92}).  It
        had {monitor} and user modes, dynamic program relocation,
        automatic memory fragmentation, and system protection.
     
        After 1968 {Xerox} bought out SDS and renamed the SDS machines
        "Xerox Data Systems" (XDS) but never actually built any.
     
        (2002-09-08)