From: Kent Karlsson (firstname.lastname@example.org)
Date: Fri Apr 07 2006 - 14:07:35 CST
Otto Stolz wrote:
> The title of the ISO 88591 series contains the term "single-byte coded
> graphic character sets". The use of control functions for the coded
> representation of composite characters is prohibited by ISO 8859,
This is mentioned because in ISO/IEC 646, the use of *control* codes,
more specifically backspace, was THE way of composing accented
characters. E.g. <A, backspace, (7-bit) circumflex> was supposed
to encode A WITH CIRCUMFLEX. The specification was incomplete,
and that aspect of ISO 646 never caught on, instead the national
variants did. Using backspace to encode composites is not allowed
in ISO/IEC 8859-x, it is likewise not allowed in ISO/IEC 10646.
> and there are no combining, or non-spacing (cf. infra), characters
The Latin/Arabic (as you note) and Latin/Thai parts contain combining
characters. There is no prohibition against combining characters.
> normally are composing (such as Fatha, Damma, Kasra). However,
They are just the "ordinary" combining characters used for Arabic.
> ISO 6937 has been an approach to large character sets by heavy
> use of composition. Quote from ISO 6937/2-1983:
> > Each accented letter or umlaut is represented by a sequence
> > of bit combinations consisting of the coded representation
> > of the relevant non-spacong diacritical mark [...], followed
> > by the coded representation of the relevant basic Latin letter
> > [...]
That text is at best misleading; I'd say it's completely wrong.
In actual fact, ISO/IEC 6937 does not encode any combining
characters, absolutely NONE whatsoever. Nor does it rely at all
on any kind of composition.
HOWEVER, it is a multibyte encoding, where lead bytes (with the
8th bit set) sort of indicate the accent of the character (but that
does not always hold true) and the trail byte (if a double-byte code)
indicates the base character (except when the trail byte is the one
But the lead byte NEVER encodes any combining character.
None, zilch, nada, niente, no way mate.
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