Request for Comments: 698 Jul 1975
NIC #32964
TELNET EXTENDED ASCII OPTION
- 1. Command Name and Code.
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- EXTEND-ASCII 17
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- 2. Command Meanings.
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- IAC WILL EXTEND-ASCII
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- The sender of this command requests Permission to begin
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- transmitting, or confirms that it may now begin transmitting
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- extended ASCII, where additional 'control' bits are added to
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- normal ASCII, which are treated sPecially by certain programs on
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- the host computer.
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- IAC WON'T EXTEND-ASCII
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- If the connection is already being operated in extended ASCII
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- mode, the sender of this command demands that the receiver begin
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- transmitting data characters in standard NVT ASCII. If the
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- connection is not already being operated in extended ASCII mode,
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- The sender of this command refuses to begin transmitting extended
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- ASCII.
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- IAC DO EXTEND-ASCII
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- The sender of this command requests that the receiver begin
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- transmitting,or confirms that the receiver of this command is
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- allowed to begin transmitting extended ASCII.
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- IAC DON'T EXTEND-ASCII
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- The sender of this command demands that the receiver of this
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- command stop or not start transmitting data in extended ASCII
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- mode.
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- IAC SB EXTASC
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- <high order bits (bits 15-8)><low order bits (bits 7-0)> IAC SE
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- This command transmits an extended ASCII character in the form of
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- two 8-bit bytes. Each 8-bit byte contains 8 data bits.
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-1-
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- RFC 698, NIC 32964 (July 23 1975)
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- 3. Default
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- DON'T EXTEND-ASCII
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- WON'T EXTEND-ASCII
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- i.e., only use standard NVT ASCII
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- 4. Motivation.
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- Several sites on the net, for example, SU-AI and MIT-AI, use
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- keyboards which use almost all 128 characters as printable
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- characters, and use one or more additional bits as "control' bits as
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- command modifiers or to separate textual input from command input to
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- programs. Without these additional bits, several characters cannot
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- be entered as text because they are used for control purposes, such
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- as the greek letter "beta' which on a TELNET connection is CONTROL-C
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- and is used for stopping ones job. In addition there are several
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- commonly used programs at these sites which require these additional
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- bits to be run effectively. Hence it is necessary to provide some
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- means of sending characters larger than 8 bits wide.
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- 5. Description of the option.
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- This option is to allow the transmission of extended ASCII.
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- Experience has shown that most of the time, 7-bit ASCII is typed,
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- with an occasional "control' character used. Hence, it is expected
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- normal NVT ASCII would be used for 7-bit ASCII and that
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- extended-ASCII be sent as an escape character sequence.
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- The exact meaning of these additional bits depends on the user
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- program. At SU-AI and at MIT-AI, the first two bits beyond the
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- normal 7-bit ASCII are passed on to the user program and are denoted
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- as follows.
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- Bit 8 (or 200 octal) is the CONTROL bit
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- Bit 9 (or 400 octal) is the META bit
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- (NOTE: "CONTROL' is used in a non-standard way here; that is, it
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- usually refers to codes 0-37 in NVT ASCII. CONTROL and META are
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- echoed by prefixing the normal character with 013 (integral symbol)
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- for CONTROL and 014 (plus-minus) for META. If both are present, it
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- is known as CONTROL-META and echoed as 013 014 7-bit character.)
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-2-
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- RFC 698, NIC 32964 (July 23, 1975)
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- 6. Description of Stanford Extended ASCII Characters
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- In this section, the extended graphic character set used at SU-AI is
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- described for reference, although this specific character set is not
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- required as part of the extended ASCII Telnet option. Characters
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- described as "hidden" are alternate graphic interpretations of codes
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- normally used as format effectors, used by certain typesetting
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- programs.
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- Code Graphic represented
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- 000 null (hidden vertically centered dot)
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- 001 downward arrow
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- 002 alpha (all Greek letters are lowercase)
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- 003 beta
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- 004 logical and (caret)
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- 005 logical not (dash with downward extension)
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- 006 epsilon
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- 007 pi
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- 010 lambda
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- 011 tab (hidden gamma)
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- 012 linefeed (hidden delta)
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- 013 vertical tab (hidden integral)
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- 014 formfeed (hidden plus-minus)
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- 015 carriage return (hidden circled-plus)
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- 016 infinity
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- 017 del (partial differential)
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- 020 proper subset (right-opening horseshoe)
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- 021 proper superset (left-opening horseshoe)
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- 022 intersection (down-opening horseshoe)
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- 023 union (up-opening horseshoe)
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- 024 universal quantifier (upside-down A)
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- 025 existential quantifier (backwards E)
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- 026 circled-times
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- 027 left-right double headed arrow
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- 030 underbar
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- 031 right pointing arrow
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- 032 tilde
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- 033 not-equal
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- 034 less-than-or-equal
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- 035 greater-than-or-equal
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- 036 equivalence (column of 3 horizontal bars)
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- 037 logical or (V shape)
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- 040-135 as in standard ASCII
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-3-
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- RFC 698, NIC 32964 (July 23, 1975)
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- 136 upward pointing arrow
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- 137 left pointing arrow
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- 140-174 as in standard ASCII
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- 175 altmode (prints as lozenge)
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- 176 right brace
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- 177 rubout (hidden circumflex)
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-4-