RFC 2237 (rfc2237) - Page 2 of 6

Japanese Character Encoding for Internet Messages

Alternative Format: Original Text Document
< Previous
Next >
RFC 2237              Japanese Character Encoding          November 1997


   supplementary Japanese graphic character set for information
   interchange". Most Japanese characters which are used in regular
   electronic mail in most cases can be accommodated in JIS X 0201, JIS
   X 0208 and JIS X 0212.

   Also it is recognized that there is a tendency to use Unicode,
   however, Unicode is not yet widely used and there is a certain
   limitation with old electronic mail system. Furthermore, the purpose
   of this comment is to add the capability of writing out JIS X 0212.

   This comment does not describe any representation of iso-2022-jp-1
   version information in addition to JIS X 0212 support.

4. Description

   In "ISO-2022-JP-1" text, the initial character code of the message is
   in ASCII. The "double-byte-seq"(see "Format Syntax" section) (ESC "$"
   "B" / ESC "$" "@" / ESC "$" "(" "D") is the only designator that
   indicates that the following character is double-byte, and it is
   valid until another escape sequence appears.  It is very discouraged
   to use (ESC "$" "@") for double byte character encoding, new
   implementation SHOULD use only (ESC "$" "B") for double byte encoding
   instead.

   The end of "ISO-2022-JP-1" text MUST be in ASCII. Also it is strongly
   recommended to back up to the ASCII at the end of each line rather
   than JIS X 0201-Roman if there is any none ASCII character in middle
   of a line.

   Since "ISO-2022-JP-1" is designed to add the capability of writing
   out JIS X 0212, if the message does not contain none of JIS X 0212
   characters. "ISO-2022-JP" text MUST BE used.

   JIS X 0201-Roman is not identical to the ASCII with two different
   characters.

   The following list are the escape sequences and character sets that
   can be used in "ISO-2022-JP-1" text. The registered number in the ISO
   2375 Register which allow double-byte ideographic scripts to be
   encoded within ISO/IEC 2022 code structure is indicated as reg#
   below.

   reg# character set     ESC sequence                  designated to
   6    ASCII             ESC 2/8 4/2                   ESC ( B    G0
   42   JIS X 0208-1978   ESC 2/4 4/0                   ESC $ @    G0
   87   JIS X 0208-1983   ESC 2/4 4/2                   ESC $ B    G0
   14   JIS X 0201-Roman  ESC 2/8 4/10                  ESC ( J    G0
   159  JIS X 0212-1990   ESC 2/4 2/8 4/4               ESC $ ( D  G0



Tamaru                       Informational
< Previous
Next >