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Translator: Guodagang Guodagang@tyut.edu.cn)
Translation time: 2001-11-7
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Request for Comments: 698 Jul 1975
NIC # 32964
Telnet extension ASCII option
(RFC698 - Telnet Extended ASCII Option)
1. Command name and code
Extend-ASCII 17
2. Command meaning
IAC WILL EXTEND-ASCII
The transmitter request of this command starts the license instruction that is transmitted, or confirms that the transmission extension ASCII characters can now be started.
. Here, the 'control' bit is added to the usual ASCII characters, and some programs on the host will be specific.
Treatment.
Iac Won't extend-ASCII
If the connection has been extended ASCII mode, the transmitter of the command requires the receiver to standard NVT.
ASCII begins to transmit data character sets. If you have used a non-extended ASCII mode to operate, the sender of the command
Refuse to start sending an extended ASCII.
Iac Do Extend-ASCII
The transmitter of this command requires the receiver to start transmitting or confirming that the receiver of the command is allowed to start transmission expansion.
ASCII.
Iac Don't extend-ASCII
The transmitter of this command requires the receiver of the command to stop or not start to extend the ASCII mode.
IAC SB EXTASC
This command transmits an extended ASCII character in the form of two eight-bit bytes. Each eight-bit byte contains eight data
Bit.
3. Default
Don't extend-ASCII
Won't extend-ASCII
That is, only standard NVT ASCII
4. Motivation
Some of the networks, for example, Su-ai and Mit-ai use that kind of almost all 128 characters
The keyboard of the printing character set, and uses one or more additional bit as the 'control' bit to modify or from the input
The text is separated from the command, and then it is entered to the program. If there is no additional bit, some characters will not be entered as text,
Because they have been used for control purposes, for example, in the Telnet connection, the Greek letter "Beta" is
Control-C for termination of a job. In addition, there are some access to these additional bit effectively operated.
Use the program. Therefore, it is necessary to provide a method of sending a string greater than 8 bits.
5. Option description
This option allows to transfer the expansion ASCII characters.
Experience shows that in most cases, 7 ASCII characters are typical, occasionally use 'control' strings. therefore,
It can be seen that the standard NVT ASCII will use 7-bit ASCII characters, and the expansion of the ASCII character is used to represent the character.
Column.
The precise meaning of these additional bits depends on the program of the user segment. In Su-ai and Mit-Ai, the usual 7 ASCII
The first two bits of the string are passed to the user-end program, indicating as follows. Bit 8 (or 200 Octa) is a Control bit
Bit 9 (or 400 octa) is a META bit
(Note: "Control" usage is not standard; that is, it usually refers to NVT ASCII
Code 0-37. Control and Meta can represent representatives in front of the characters, such as 013 before character (whole
Number of markers indicate Control, add 014 (plus - minus) to represent META before character. If the two appear simultaneously,
Control-meta, its representation is 013 014 7 bit character. )
6. Stanford extension ASCII character set description
In this section, the description of the extended graphic character set used in SU-Ai is shown in the appendix, although this special character set is for
The extended ASCII Telnet option section is not required. Described character set, such as "hidden", in the typographic program
Make a format control, and make an image notes for usual symbols.
Code graphic represented
000 space bar (implied with vertical center)
001 downward arrow
002 Alpha (all Greek letters are lowercase)
003 Beta
004 Logic and (Die Zhao Symbol)
005 logic is not (with the downward expansion)
006 EPSILON
007 PI
010 lambda
011 playing character (implied with gamma)
012 Removal (dark Delta)
013 vertical tab (dark integral)
014 change page (implied with a log)
015 Enter (with a plus picture with a circle)
016 infinity
017 Delete key (local differential)
020 subset (included)
021 replenishment (belong to)
022 intersection (and)
023 combined (pay)
024 universal quantifier (pour a)
025 exists quantifiers (pour E)
026 draws a number of circles
Bidirectional arrow around 027
030 Underline
031 to the right arrow
032 TILDE
033 is not equal
034 less than or equal
035 is greater than or equal
036 equivalent
037 logic or (V)
040-135 is a standard ASCII character
136 down arrow
137 to the left arrow
140-174 is standard ASCII characters
175 alt mode (print diamond)
176 right parentheses
177 dash (implied with waves)
RFC698 - ELNET Extended ASCII Option Telnet extension ASCII options
2
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