Source : Free On-Line Dictionary of Computing

Hewlett Packard Multi Processing Executive
     
         (HP-MPE) The standard {operating system} on
        all {HP3000} {minicomputers}, in the same way that HP9000
        computers run {HP-UX}.
     
        Current version: MPE/IX Version 5.5.04, as of 1998-02-17.
     
        (1998-02-17)