TTY_DEFCHAR sets the default characteristics for terminals, using
    a code derived by summing the following hexadecimal values:

    Characteristic   Value (Hex)     Function

    PASSALL                 1        Passall.
    NOECHO                  2        Noecho mode.
    NOTYPEAHEAD             4        No type-ahead buffer.
    ESCAPE                  8        Escape sequence processing.
    HOSTSYNC               10        Host can send XON and XOFF.
    TTSYNC                 20        Terminal can send XON and XOFF.
    SCRIPT                 40        Internal use only.
    LOWER                  80        Lowercase.
    MECHTAB               100        Mechanical tabs.
    WRAP                  200        Wraparound at end of line.
    CRFILL                400        Perform carriage return fill.
    LFFILL                800        Perform line feed fill.
    SCOPE                1000        Terminal is a scope.
    REMOTE               2000        Internal use only.
    EIGHTBIT             8000        Eight-bit terminal.
    MBXDSABL            10000        Disable mailbox.
    NOBRDCST            20000        Prohibit broadcast.
    READSYNC            40000        XON and XOFF on reads.
    MECHFORM            80000        Mechanical form feeds.
    HALFDUP            100000        Set for half-duplex operation.
    MODEM              200000        Set for modem signals.
    PAGE             FF000000        Page size. Default is 24.

    Do not set the CRFILL or LRFILL characteristic as the default in
    TTY_DEFCHAR.

    Where a condition is false, the value is 0.

    The upper byte is the page length. The default characteristics
    are 24 lines per page, terminal synchronization, wraparound,
    lowercase, scope, and full-duplex.