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Both UTF-16 and UCS-2 encode code points in this range as single 16-bit code units that are numerically equal to the corresponding code points. These code points in the Basic Multilingual Plane (BMP) are the only code points that can be represented in UCS-2.
As of Unicode version 16.0, there are 155,063 characters with code points, covering 168 modern and historical scripts, as well as multiple symbol sets.This article includes the 1,062 characters in the Multilingual European Character Set 2 subset, and some additional related characters.
All code points in the BMP are accessed as a single code unit in UTF-16 encoding and can be encoded in one, two or three bytes in UTF-8. Code points in planes 1 through 16 (the supplementary planes) are accessed as surrogate pairs in UTF-16 and encoded in four bytes in UTF-8.
The UCS includes 2048 code points in the Basic Multilingual Plane (BMP) for surrogate code point pairs. Together these surrogates allow any code point in the sixteen other planes to be addressed by using two surrogate code points. This provides a simple built-in method for encoding the 20.1 bit UCS within a 16 bit encoding such as UTF-16.
A range of code points in the S (Special) Zone of the BMP remains unassigned to characters. UCS-2 disallows use of code values for these code points, but UTF-16 allows their use in pairs. Unicode also adopted UTF-16, but in Unicode terminology, the high-half zone elements become "high surrogates" and the low-half zone elements become "low ...
A code point, codepoint or code ... (= 2 16) code points. Thus the total size of the Unicode code space is 17 × 65,536 = 1,114,112. ... while in the UTF-8 encoding ...
A code point is represented by a sequence of code units. The mapping is defined by the encoding. Thus, the number of code units required to represent a code point depends on the encoding: UTF-8: code points map to a sequence of one, two, three or four code units. UTF-16: code units are twice as long as 8-bit code units.
The last code point in Unicode is the last code point in plane 16, U+10FFFF. As of Unicode version 16.0, 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 2 20 code points (16 planes) as pairs of words, plus the BMP as a single word. [2]