CODEWITHSUNDEEP
unicodenoncharacter
skyking
skyking

Reputation: 14394

Why are the two last points on supplemental PUAs excluded?

The supplemental PUAs (F0000-FFFFD and 100000 10FFFD) has explicitely excluded FFFFE, FFFFF, 10FFFE and 10FFFF by defining them as non-characters. Why was this done? Without this they would be nice 65536-point blocks.

Upvotes: 0

Views: 36

Answers (1)

一二三
一二三

Reputation: 21249

The last two code points of each of the supplementary planes are reserved as "noncharacter" code points for "internal" use (see this section of the Unicode FAQ). They may be used as private, proprietary markers within your application/system – but they are not intended to be interchanged between systems (unlike other PUA code points).

As for why these code points were chosen: they were defined in Unicode 2.0 (1996) but no rationale was given in the standard (and the historical documents in the register are not available online). One possibility is that they are easy to identify: all 0x••••FFFE and 0x••••FFFF code points are noncharacters.

Upvotes: 1

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