TELNET EXTENDED ASCII OPTION

1 Command Name and Code.

EXTEND-ASCII 17

2 Command Meanings.

IAC WILL EXTEND-ASCII

The sender of this command requests Permission to begin

transmitting, or confirms that it may now begin transmitting

extended ASCII, where additional 'control' bits are added to

normal ASCII, which are treated sPecially by certain programs on

the host computer.

IAC WON'T EXTEND-ASCII

If the connection is already being operated in extended ASCII

mode, the sender of this command demands that the receiver begin

transmitting data characters in standard NVT ASCII. If the

connection is not already being operated in extended ASCII mode,

The sender of this command refuses to begin transmitting extended

ASCII.

IAC DO EXTEND-ASCII

The sender of this command requests that the receiver begin

transmitting,or confirms that the receiver of this command is

allowed to begin transmitting extended ASCII.

IAC DON'T EXTEND-ASCII

The sender of this command demands that the receiver of this

command stop or not start transmitting data in extended ASCII

mode.

IAC SB EXTASC

<high order bits (bits 15-8)><low order bits (bits 7-0)> IAC SE

This command transmits an extended ASCII character in the form of

two 8-bit bytes. Each 8-bit byte contains 8 data bits.

                                  -1-

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TELNET EXTENDED ASCII OPTION

RFC 698, NIC 32964 (July 23 1975)

3 Default

DON'T EXTEND-ASCII

WON'T EXTEND-ASCII

i.e., only use standard NVT ASCII

4 Motivation.

Several sites on the net, for example, SU-AI and MIT-AI, use

keyboards which use almost all 128 characters as printable

characters, and use one or more additional bits as "control' bits as

command modifiers or to separate textual input from command input to

programs. Without these additional bits, several characters cannot

be entered as text because they are used for control purposes, such

as the greek letter "beta' which on a TELNET connection is CONTROL-C

and is used for stopping ones job. In addition there are several

commonly used programs at these sites which require these additional

bits to be run effectively. Hence it is necessary to provide some

means 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 expected

normal NVT ASCII would be used for 7-bit ASCII and that

extended-ASCII be sent as an escape character sequence.

The exact meaning of these additional bits depends on the user

program. At SU-AI and at MIT-AI, the first two bits beyond the

normal 7-bit ASCII are passed on to the user program and are denoted

as follows.

Bit 8 (or 200 octal) is the CONTROL bit

Bit 9 (or 400 octal) is the META bit

(NOTE: "CONTROL' is used in a non-standard way here; that is, it

usually refers to codes 0-37 in NVT ASCII. CONTROL and META are

echoed by prefixing the normal character with 013 (integral symbol)

for CONTROL and 014 (plus-minus) for META. If both are present, it

is known as CONTROL-META and echoed as 013 014 7-bit character.)

                                -2-

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TELNET EXTENDED ASCII OPTION

RFC 698, NIC 32964 (July 23, 1975)

6 Description of Stanford Extended ASCII Characters

In this section, the extended graphic character set used at SU-AI is

described for reference, although this specific character set is not

required as part of the extended ASCII Telnet option. Characters

described as "hidden" are alternate graphic interpretations of codes

normally used as format effectors, used by certain typesetting

programs.

Code Graphic represented

000 null (hidden vertically centered dot)

001 downward arrow

002 alpha (all Greek letters are lowercase)

003 beta

004 logical and (caret)

005 logical not (dash with downward extension)

006 epsilon

007 pi

010 lambda

011 tab (hidden gamma)

012 linefeed (hidden delta)

013 vertical tab (hidden integral)

014 formfeed (hidden plus-minus)

015 carriage return (hidden circled-plus)

016 infinity

017 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-times

027 left-right double headed arrow

030 underbar

031 right pointing arrow

032 tilde

033 not-equal

034 less-than-or-equal

035 greater-than-or-equal

036 equivalence (column of 3 horizontal bars)

037 logical or (V shape)

040-135 as in standard ASCII

                               -3-

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TELNET EXTENDED ASCII OPTION

RFC 698, NIC 32964 (July 23, 1975)

136 upward pointing arrow

137 left pointing arrow

140-174 as in standard ASCII

175 altmode (prints as lozenge)

176 right brace

177 rubout (hidden circumflex)

                                -4-