Re: How many possible characters? (was: Re: Names of planes...)

From: Asmus Freytag (
Date: Wed Jul 12 2000 - 04:00:38 EDT

At 09:55 PM 7/11/00 -0800, Doug Ewell wrote:
>BTW, it's interesting that the FAQ claims this is "for no good reason,"

The exclusion came from Unicode (which was then 64K only) and was agreed to
by ISO, but with an "if we do this for one plane, we do this for all planes".
approach. I don't remember that any other reasoning was given at the time,
but in the big Unicode/ISO merger not all details where always hashed out -
the parties were happy in the end to have a living, breathing compromise
to build on. The expert or country putting forward the request may in fact
have had their own good reasons to do so....

>I can think of a good reason to at least exclude the
>characters ending in FFFE: if expressed in UTF-32 little-endian and
>appearing at the beginning of a file, they could fool an auto-detection
>scheme into thinking the file is UTF-16 big-endian.

There are a few other design features in Unicode that initially were more
fortuitous than deliberate. Doug makes a good point that it's often more
productive to point out these benefits than the imputed absence of
forethought ;-).


PS: After spending some delightful half-hour dusting off old paper
documents, I cannot find any paper that actually deals with the exclusions
in higher planes. I've found editorial comments by the US requesting
language changes in the relevant section, but those changes do not seem to
imply that other planes were contemplated. The same is true for the minutes
of previous meetings covering the topic of 0xFFFE and 0xFFFF.

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