Re: Canonical Combining Classes

From: Kenneth Whistler (
Date: Wed Jan 12 2000 - 21:51:13 EST

John Hudson asked:

> The following Canonical Combining Classes have one or more members in the
> current UnicodeData.txt file, but are not defined on the UnicodeData.hmtl
> page. Where can I find the definitions for these classes?
> 11
> 12
> 13
> 130
> 132

These are all "fixed position classes". The intent on these was to
indicate combining marks that always come in some defined position,
and don't interact and combine in stacks. A major change between
Unicode 2.0 and Unicode 3.0 was to bleed off many of the fixed position
classes into combining class 0 where there really was no interaction
between them; only a relatively small handful of the fixed position
classes were retained -- with the numbers unchanged insofar as possible.

This change simplified a number of things for normalization and was done
because there didn't seem to be any strong reason to keep all the
fixed position class assignments. They made no real difference for

The printed text of Table 4-3 Combining Classes in Unicode 3.0 will
clarify a lot of this for people.


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