Plane (Unicode)

Uncommon card · No. 182634

In the Unicode standard, a plane is a contiguous group of 65,536 (216) code points. There are 17 planes, identified by the numbers 0 to 16, which corresponds with the possible values 00–1016 of the first two positions in six position hexadecimal format (U+hhhhhh). Plane 0 is the Basic Multilingual Plane (BMP), which contains most commonly used characters. The higher planes 1 through 16 are called "supplementary planes". The last code point in Unicode is the last code point in plane 16, U+10FFFF. As of Unicode version 18.0, five of the planes have assigned code points (characters), and seven are named. The limit of 17 planes is due to UTF-16, which can encode 220 code points (16 planes) as pairs of words, plus the BMP as a single word. UTF-8 was designed with a much larger limit of 231 (2,147,483,648) code points (32,768 planes), and would still be able to encode 221 (2,097,152) code points (32 planes) even under the current limit of 4 bytes. The 17 planes can accommodate 1,114,112 code...

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