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Network Working Group W. Hathaway Request for Comments: 135 AMES NIC: 6712 29 April 1971 Updates: 110

                      Response to NWG/RFC #110
 (Conventions for Using an IBM 2741 Terminal as a User Console for
                  Access to Network Server Hosts)

 I would like to propose the following conventions to replace the ones
 proposed in RFC #110.  The original conventions suffer from lack of
 consideration of the correspondence 2741 and what I feel are
 inconsistencies and considerable difficulty of use.  (The 2741
 terminal with correspondence keyboard does not have all of the
 standard characters, notably:

    less than       <
    greater than    >
    logical not    [1]
    vertical bar    |

 Thus we must not use any of these characters in our conventions if we
 wish to support the correspondence 2741.)

 The dedication of certain characters to special functions involves a
 trade-off: the convenience of having the function as a single key
 versus the inconvenience of having to use two keys to enter the
 character as data.  I believe that only two of the special functions
 listed in RFC #110 justify the dedication of a key: the "character
 escape" function and the "character delete" function.  For the
 "character escape" function I recommend the cent sign [2], as this
 character is on both the regular and correspondence 2741 terminals
 and is not in the ASCII character set.  For the "character delete"
 function I recommend the backspace key for obvious reasons.  While
 there is some need to be able to enter the character "backspace" (as
 for underscoring output etc.,) I feel that the trade-off mentioned
 above clearly indicates a single key "character delete" would be much
 more valuable than a single key "backspace" and a two key "character
 delete."

 For the other special functions I recommend two key combinations,
 consisting of "character escape" [2] and a key to define the
 function.  These are summarized below:

Hathaway [Page 1]  RFC 135 Response to NWG/RFC #110 29 April 1971

    character escape        [2]
    character delete        backspace
    system delete           [2]$
    line delete             [2]# or [2]#NL
    logical line end        [2];
    line continuation       [2]NL
    ASCII control           [2]@

 The option in "line delete" is to allow the user to enter a new line
 (NL) immediately after the "line delete" to line up margins without
 entering a null line; to enter a null line after a "line delete"
 would require two NL characters.

 The two new functions defined above, "line continuation" and "ASCII
 control," are used as follows.  The "line continuation" is used to
 enter a line which is longer than the 2741 carriage (or the margin
 placement) will permit.  It can be looked on as the complement of the
 "logical line end" in that is allows you to enter one logical line on
 several physical lines.

 The use of the "ASCII control" function requires some background.
 There are of course many characters in ASCII which are keyed as
 combinations of "control" and another key.  The "character escape"
 function may be used to handle these control characters as follows: a
 "character escape" followed by a letter will be the equivalent of the
 ASCII "control" "letter", written as Xc (where X is the letter).
 This will greatly simplify the conventions for users, as they will
 simply key "[2]A" where they are used to using Ac and so forth.  For
 completeness, however, there needs to be a way to key the additional
 control characters which require both "control" and "shift" in
 addition to a letter (such as ESC, which is SHIFT Mc).  Further it is
 desirable that a more mnemonic system be provided for the non-
 Teletype user, who knows he wants a LF but does not know that it is a
 Jc.  To satisfy both of these needs I recommend the "ASCII control"
 special function, which is used to enter any of the ASCII control
 character as "[2]@" followed by the standard two or three character
 abbreviation.  Thus "escape" would be [2]@ESC, "line feed" would be
 [2]@LF, and so forth.  The use of the variable length abbreviation
 does not introduce any ambiguity, although from an implementation
 standpoint it may be advantageous to use the two character
 abbreviation proposed in RFC #110.

 Finally we must be able to enter the eight ASCII graphics which do
 not appear on either 2741 terminal, as well as the "cent sign" and
 "backspace" themselves (without their special functions).  For these
 I recommend the following:

Hathaway [Page 2]  RFC 135 Response to NWG/RFC #110 29 April 1971

    [2](            for     [
    [2])            for     ]
    [2]6            for     {
    [2]9            for     }
    [2]/            for     \
    [2]'            for     '
    [2]"            for     ^
    [2]-            for     ~
    [2][2]          for     [2]
    [2]backspace    for     backspace

 Note that the characters "<" and ">" do not appear on the
 correspondence 2741 and hence should not be used.

Endnotes

 [1] logical not

 [2] cent sign

        [This RFC was put into machine readable form for entry]
        [into the online RFC archives by Lorrie Shiota, 10/02]

Hathaway [Page 3]