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Request for Comments: 698                                              Jul 1975NIC #32964TELNET EXTENDED ASCII OPTION1. Command Name and Code.EXTEND-ASCII 172. Command Meanings.IAC WILL EXTEND-ASCIIThe sender of this command requests Permission to begintransmitting, or confirms that it may now begin transmittingextended ASCII, where additional 'control' bits are added tonormal ASCII, which are treated sPecially by certain programs onthe host computer.IAC WON'T EXTEND-ASCIIIf the connection is already being operated in extended ASCIImode, the sender of this command demands that the receiver begintransmitting data characters in standard NVT ASCII. If theconnection is not already being operated in extended ASCII mode,The sender of this command refuses to begin transmitting extendedASCII.IAC DO EXTEND-ASCIIThe sender of this command requests that the receiver begintransmitting,or confirms that the receiver of this command isallowed to begin transmitting extended ASCII.IAC DON'T EXTEND-ASCIIThe sender of this command demands that the receiver of thiscommand stop or not start transmitting data in extended ASCIImode.IAC SB EXTASC<high order bits (bits 15-8)><low order bits (bits 7-0)> IAC SEThis command transmits an extended ASCII character in the form oftwo 8-bit bytes. Each 8-bit byte contains 8 data bits.                                  -1-

TELNET EXTENDED ASCII OPTIONRFC 698, NIC 32964 (July 23 1975)3. DefaultDON'T EXTEND-ASCIIWON'T EXTEND-ASCIIi.e., only use standard NVT ASCII4. Motivation.Several sites on the net, for example, SU-AI and MIT-AI, usekeyboards which use almost all 128 characters as printablecharacters, and use one or more additional bits as "control' bits ascommand modifiers or to separate textual input from command input toprograms. Without these additional bits, several characters cannotbe entered as text because they are used for control purposes, suchas the greek letter "beta' which on a TELNET connection is CONTROL-Cand is used for stopping ones job. In addition there are severalcommonly used programs at these sites which require these additionalbits to be run effectively. Hence it is necessary to provide somemeans of sending characters larger than 8 bits wide.5. Description of the option.This option is to allow the transmission of extended ASCII.Experience has shown that most of the time, 7-bit ASCII is typed,with an occasional "control' character used. Hence, it is expectednormal NVT ASCII would be used for 7-bit ASCII and thatextended-ASCII be sent as an escape character sequence.The exact meaning of these additional bits depends on the userprogram. At SU-AI and at MIT-AI, the first two bits beyond thenormal 7-bit ASCII are passed on to the user program and are denotedas follows.Bit 8 (or 200 octal) is the CONTROL bitBit 9 (or 400 octal) is the META bit(NOTE: "CONTROL' is used in a non-standard way here; that is, itusually refers to codes 0-37 in NVT ASCII. CONTROL and META areechoed by prefixing the normal character with 013 (integral symbol)for CONTROL and 014 (plus-minus) for META. If both are present, itis known as CONTROL-META and echoed as 013 014 7-bit character.)                                -2-

TELNET EXTENDED ASCII OPTIONRFC 698, NIC 32964 (July 23, 1975)6. Description of Stanford Extended ASCII CharactersIn this section, the extended graphic character set used at SU-AI isdescribed for reference, although this specific character set is notrequired as part of the extended ASCII Telnet option. Charactersdescribed as "hidden" are alternate graphic interpretations of codesnormally used as format effectors, used by certain typesettingprograms.Code Graphic represented000 null (hidden vertically centered dot)001 downward arrow002 alpha (all Greek letters are lowercase)003 beta004 logical and (caret)005 logical not (dash with downward extension)006 epsilon007 pi010 lambda011 tab (hidden gamma)012 linefeed (hidden delta)013 vertical tab (hidden integral)014 formfeed (hidden plus-minus)015 carriage return (hidden circled-plus)016 infinity017 del (partial differential)020 proper subset (right-opening horseshoe)021 proper superset (left-opening horseshoe)022 intersection (down-opening horseshoe)023 union (up-opening horseshoe)024 universal quantifier (upside-down A)025 existential quantifier (backwards E)026 circled-times027 left-right double headed arrow030 underbar031 right pointing arrow032 tilde033 not-equal034 less-than-or-equal035 greater-than-or-equal036 equivalence (column of 3 horizontal bars)037 logical or (V shape)040-135 as in standard ASCII                               -3-

TELNET EXTENDED ASCII OPTIONRFC 698, NIC 32964 (July 23, 1975)136 upward pointing arrow137 left pointing arrow140-174 as in standard ASCII175 altmode (prints as lozenge)176 right brace177 rubout (hidden circumflex)                                -4-