/sys$common/syshlp/helplib.hlb SET, TERMINAL, Qualifiers, /DEC_CRT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /DEC_CRT[=(value1,value2,value3)]
       /NODEC_CRT[=(value1,value2,value3)]

    Controls whether the terminal conforms to DIGITAL VT100-,
    VT200-, VT300-, VT400-, or VT500-family standards and supports
    the minimum standards, including the additional DIGITAL escape
    sequences.

    You can specify one of the following values:

    1           Requests that the DEC_CRT terminal characteristic be
    (default)   set.

    2           Requests that the DEC_CRT2 terminal characteristic be
                set.

    3           Requests that the DEC_CRT3 terminal characteristic
                be set. A level 3 terminal supports the following
                additional features:

                o  A status line (line 25, at the bottom of the
                   screen)

                o  The ISO Latin1 character set

                o  Terminal state interrogation (describes what state
                   your terminal is in)

    4           Requests that the DEC_CRT4 terminal characteristic
                be set. A level 4 terminal supports the following
                additional features:

                o  Extended keyboard

                o  Key position mode

                o  Secure reset

                o  Novice mode

                o  Selective erase

                o  On-line transaction processing (OLTP) features:

                   -  Page memory

                   -  Rectangular editing

                   -  Text macros

                   -  Data integrity reports

    Note that DEC_CRT2, DEC_CRT3, and DEC_CRT4 are supersets of DEC_
    CRT. Clearing DEC_CRT causes DEC_CRT2, DEC_CRT3, and DEC_CRT4
    to be cleared. Similarly, setting DEC_CRT4 causes all subsets of
    DEC_CRT4 (including ANSI_CRT) to be set.