Subject: Re: DO YOU KNOW IS10646 OR UNICODE

From: Ross Paterson <[email-masked]>
Date: Fri, 29 Jan 1993 11:58:16 GMT

Helena Wong <[email-masked]> asks:
>      Could anybody tell me about "the ISO/IEC DP10646 Multiple Octet Coded
> Character Set,  which now becomes International Standard IS10646".

[Maybe this should be in the FAQ list.]

ISO 10646 and Unicode began as competing standards.  The ISO philosophy
was approximately a disjoint union of national standards, yielding
a 32-bit code, while Unicode aimed at unifying identical characters
from different variants of the same script, to give a 16-bit code.
They have since been unified: ISO 10646 has two forms, a 32-bit form
and a 16-bit form.  The 16-bit form will be code-for-code identical with
Unicode, though some of the official names of characters differ.  It is
also a subset of the 32-bit form, the rest of which is so far undefined.
Perhaps it will be filled with presentation forms.

The overall layout of this unified 16-bit code is:

        0000 - 1FFF     Alphabets
        2000 - 2FFF     Symbols and Punctuation
        3000 - 4DFF     CJK Auxiliary
        4E00 - 9FFF     Unified Ideographs (20,902)
        A000 - DFFF     Reserved for future assignment
        E000 - FFFF     Restricted use

The only backward compatability is that 0000-00FF is identical to ISO
Latin-1, of which ASCII is the lower half.  (or maybe some non-Latin
alphabets are copies of existing standards at some offset.)

ISO standards are usually copyrighted and sold.  I don't know if this one
is available yet.  Unicode is fully described in

        "The Unicode standard : worldwide character encoding"
        (vols 1 & 2) the Unicode Consortium,
        Reading MA : Addison-Wesley, 1991-1992
        ISBN: 0-201-56788-1 (pbk. : v. 1)
        ISBN: 0-201-60845-6 (pbk. : v. 2)
        LC: QA76.76.C53U6

The volumes cost US$39.95 each.  Unicode is also making stuff available
for anonymous FTP; in unicode.org:pub/MappingTables/ you will find

        cjkxref.fix     a cross-reference between Unicode and various CJK
                        standards for Hanzi.  (Look through the CCNET-L
                        archive from last November for messages about
                        the format of this file.)
        namesall.lst    a list of official names of other characters.

In metis.com:pub/csmaps/ are more cross-reference tables, including CJK
punctuation, etc, but not checked as thoroughly as the above files.

There have also been some some proposals for variable-length encodings
of Unicode and ISO 10646.  One of them, UTF-FSS, is used as the standard
format of text files in Plan-9, an experimental next-generation Unix.
In this coding, existing ASCII files are also UTF files.  For more info,
see research.att.com:research/memo/utfman.{ps,asc} (log in as netlib).
--
Ross Paterson <[email-masked]>
Department of Computing, Imperial College, London SW7