Re: plane business

From: Rick McGowan (rick@unicode.org)
Date: Mon Oct 01 2001 - 20:44:23 EDT


Some brief and not complete answers follow.

> I'm trying to get a grasp on exactly how many planes
> are defined in Unicode
> [...]
> How many planes are defined in Unicode 3.1?

There are 17 planes, and everything will be re-written to reflect that,
eventually. Most of the planes are empty (except for the non-characters).
And two of the planes are full of user-defined private-use characters.

The ISO 10646 standard is being revised (or has been already?) so that
Unicode and 10646 all agree on 17 planes.

Appendix C of Unicode 3.0 talks about planes.

> BTW, it doesn't make sense for every code position
> ending in FFFF or FFFE to be a non character.

Perhaps it doesn't. But as I have said before, in other places:
"If everything made sense, we wouldn't need surrealism to explain it."

> 32 non character
> code values in the arabic presentation form block

Which are those? Can you point to precise codepoint values?

> Why isn't the same rule applied to the hidden non
> characters, so that every code value ending in FDD0 to
> FDEF is also a non character? Is it to contribute to
> their hidden nature?

I don't understand this. What is special about those codepoints?



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