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Re: ISO 2022

1991-11-12 21:56:11

 I remain concerned that there needs to be more explanation and definition
of the ISO-2022-JP encodings.  I would be satisfied with explicit references
to the JIS documents, explicit reference to the ISO-2022 document, and some
definition of what the initial character set and state are for that type.

The following is a definition of the encoding (or codeset) used
in Japanese 821/822 networks.

  Announcer sequences ESC 2/0 4/1, ESC 2/0 4/8 and ESC 2/0 4/10
  are implicitly assumed.  These announcer sequences must not
  appear as a part of the data.
  (They mean ``Use G0 only and no locking-shifts are allowed,''
  ``Use 94 characters sets only'' and ``Use 7-bits.'')

  Designation sequences ESC 2/8 4/2, ESC 2/8 4/10, ESC 2/4 4/0
  and ESC 2/4 4/2 are allowed.  Any other designation sequences
  are not allowed.
  (Each escape sequence designates:
    ESC 2/8 4/2:   ASCII.
    ESC 2/8 4/10:  Left half of JIS X0201.  (Japanese version of 646)
    ESC 2/4 4/0:   JIS C6226-1978; so-called ``Old JIS Kanji.''
    ESC 2/4 4/2:   JIS X0208-1983; so-called ``New JIS Kanji.'')

  Any other escape sequences are not allowed.

  At the beginning, ESC 2/8 4/2 or ESC 2/8 4/10 may be omitted.

  As an exception to 2022, the following rule is applied:
    Three bit combinations 0/10, 0/13 and 2/0 can appear only
    when a single byte coded character set is designated to G0.
    I.e., these bit combinations must not appear when a multi
    byte coded character set is designated to G0.
  (This rule forces that each line starts and terminates in a
  ``single byte designation state'' and that the space is handled
  as if it is a member of 94 characters single byte graphics sets.)

I don't know this kind of information is appear in a written documents,
but I believe that the above definition can be agreed on between
Japanese experts.

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