Source : Free On-Line Dictionary of Computing

Decus cpp
     
        An almost-{ANSI C} {preprocessor} by Martin Minow.  It is
        shipped with {X11R5} (contrib/util/cpp) because some systems
        don't have a working {cpp}.
     
        It runs on {VMS} ({Vax C}, {Decus C}), {RSX-11M}, {RSTS/E},
        {P/OS}, {RT11}, {A/UX} and {Apollo Domain}/IX 9.6 and is
        highly portable.
     
        (1994-11-03)