Japanese Character Encoding for Internet Messages (RFC1468)
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2019-Feb-10
Internet Society Requests For Comment (RFCs)
J. Murai: AUTHOR [+2]
This document describes the encoding used in electronic mail [RFC822] and network news [RFC1036] messages in several Japanese networks. This memo provides information for the Internet community. It does not specify an Internet standard.
Network Working Group J. Murai Request for Comments: 1468 Keio University M. Crispin Panda Programming E. van der Poel June 1993
Japanese Character Encoding for Internet Messages
Status of this Memo
This memo provides information for the Internet community. It does not specify an Internet standard. Distribution of this memo is unlimited.
This document describes the encoding used in electronic mail [RFC822] and network news [RFC1036] messages in several Japanese networks. It was first specified by and used in JUNET [JUNET]. The encoding is now also widely used in Japanese IP communities.
The name given to this encoding is "ISO-2022-JP", which is intended to be used in the "charset" parameter field of MIME headers (see [MIME1] and [MIME2]).
The text starts in ASCII [ASCII], and switches to Japanese characters through an escape sequence. For example, the escape sequence ESC $ B (three bytes, hexadecimal values: 1B 24 42) indicates that the bytes following this escape sequence are Japanese characters, which are encoded in two bytes each. To switch back to ASCII, the escape sequence ESC ( B is used.
The following table gives the escape sequences and the character sets used in ISO-2022-JP messages. The ISOREG number is the registration number in ISO’s registry [ISOREG].
Esc Seq Character Set ISOREG
ESC ( B ASCII 6 ESC ( J JIS X 0201-1976 ("Roman" set) 14 ESC $ @ JIS X 0208-1978 42 ESC $ B JIS X 0208-1983 87
Note that JIS X 0208 was called JIS C 6226 until the name was changed
Murai, Crispin & van der Poel [Page 1]
RFC 1468 Japanese Character Encoding for Internet Messages June 1993
on March 1st, 1987. Likewise, JIS C 6220 was renamed JIS X 0201.
The "Roman" character set of JIS X 0201 [JISX0201] is identical to ASCII except for backslash () and tilde (˜). The backslash is replaced by the Yen sign, and the tilde is replaced by overline. This set is Japan’s national variant of ISO 646 [ISO646].
The JIS X 0208 [JISX0208] character sets consist of Kanji, Hiragana, Katakana and some other symbols and characters. Each character takes up two bytes.
For further details about the JIS Japanese national character set standards, refer to [JISX0201] and [JISX0208]. For further information about the escape sequences, see [ISO2022] and [ISOREG].
If there are JIS X 0208 characters on a line, there must be a switch to ASCII or to the "Roman" set of JIS X 0201 before the end of the line (i.e., before the CRLF). This means that the next line starts in the character set that was switched to before the end of the previous line.
Also, the text must end in ASCII.
Other restrictions are given in the Formal Syntax below.
The notational conventions used here are identical to those used in RFC 822 [RFC822].
The * (asterisk) convention is as follows:
meaning at least l and at most m somethings, with l and m taking default values of 0 and infinity, respectively.
message = headers 1*( CRLF *single-byte-char *segment single-by...