Telnet Data Entry Terminal option
RFC 731

Document Type RFC - Unknown (June 1977; No errata)
Obsoleted by RFC 732
Last updated 2013-03-02
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John Day                               Data Entry Terminal Option
June 27,1977                                            NIC 40652
                                                          RFC 731

                Telnet Data Entry Terminal Option

1.  Command Name and code:

        DET             20

2.  Command Meanings

     IAC WILL DET
     The sender of this command REQUESTS or AGREES  to  send  and
     receive subcommands to control the Data Entry Terminal.

     IAC WONT DET
     The sender of this  command  REFUSES  to  send  and  receive
     subcommands to control the Data Entry Terminal.

     IAC DO DET
     The sender of this command REQUESTS or AGREES  to  send  and
     receive subcommands to control the Data Entry Terminal.

     IAC DONT DET
     The sender of this  command  REFUSES  to  send  and  receive
     subcommands to control the Data Entry Terminal.

     The DET option  uses  five  classes  of  subcommands  1)  to
     establish   the   requirements   and   capabilities  of  the
     application and the terminal, 2) to format the  screen,  and
     to  control  the  3)  edit,  4) erasure, and 5) transmission
     functions.  The subcommands that perform these functions are
     described below.

     T__h_e_N__e_t_w_o_r_k_V__i_r_t_u_a_l_D__a_t_a_E__n_t_r_y_T__e_r_m_i_n_a_l(NVDET)

        The NVDET  consists  of  a  keyboard  and  a  rectangular
        display.   The  keyboard  is capable of generating all of
        the characters of the ASCII character set.  In  addition,
        the  keyboard may possess a number of function keys which
        when pressed cause a FN subcommand to be sent.  (Although
        most DET's will support one or  more  peripheral  devices
        such  as  a  paper  tape reader or a printer, this option

                                1


John Day                               Data Entry Terminal Option
June 27,1977                                            NIC 40652
                                                          RFC 731

        does not consider their support.  Support  of  peripheral
        devices should be treated by a separate option.)

        The screen of the data entry terminal is  a  rectangle  M
        characters  by N lines.  The values of M and N are set by
        negotiating the Output Line Width and  Output  Page  Size
        options,  respectively.   The next writing position (x,y)
        on the screen (where x is the character position and y is
        the position of the line on the screen) is indicated by a
        special display character called the cursor.  The  cursor
        may  be  moved  to  any  position  on  the screen without
        disturbing any characters already on the screen.   Cursor
        addressing   in   existing   terminals  utilizes  several
        topologies and addressing methods.  In order to make  the
        burden of implementaton as easy as possible this protocol
        supports two topologies (the finite plane and the helical
        torus)  and three addressing methods ((x,y); x and y, and
        relative  increments).   Since  the  finite  plane   with
        absolute  addressing  is  the  least  ambiguous  and  the
        easiest to translate to and from the others,  it  is  the
        default scheme used by the NVDET.  The torodial form with
        either  relative  or  absolute addressing is provided for
        convience.

        Also  the NVDET provides a mechanism for defining on  the
        screen  fields  with  special  attributes.   For example,
        characters entered into these  fields  may  be  displayed
        with  brighter intensity, highlighted by reverse video or
        blinking, or protected from  modification  by  the  user.
        This  latter  feature is one of the most heavily used for
        applications where the DET displays a form to  be  filled
        out by the user.

        The  definition  of  the   NVDET   uses   Telnet   option
        subnegotiations  to  accomplish  all  of  its  functions.
        Since none of the  ASCII  characters  sent  in  the  data
        stream  have been used to define these functions, the DET
        option can be used in a "raw" or even  "rare"  mode.   In
        circumstances  where  the  application program knows what
        kind of terminal is on the other end,  it  can  send  the
        ASCII   characters  required  to  control  functions  not
        supported by the option or an implementation.  In general
        keeping all  NVDET  functions  out  of  the  data  stream
        provides better flexibility.

     F__a_c_i_l_i_t_y_F__u_n_c_t_i_o_n_s  (for detailed semantics see Section 5.)

     IAC SB DET <DET facility subcommand><facility map> IAC SE

        where  <DET  facility  subcommand>  is  one  8-bit   byte

                                2


John Day                               Data Entry Terminal Option
June 27,1977                                            NIC 40652
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