The concept of a code point is part of Unicode's solution to a difficult conundrum faced by character encoding developers in the 1980s. The distinction between a code point and the corresponding abstract character is not pronounced in Unicode, but is evident for many other encoding schemes, where numerous code pages may exist for a single code space. However, code points may also be left reserved for future assignment (most of the Unicode code space is unassigned), or given other designated functions. An abstract character is not a graphical glyph but a unit of textual data. See comparison of Unicode encodings for details.Ĭode points are normally assigned to abstract characters. display a character via different glyphs.įor Unicode, the particular sequence of bits is called a code unit – for the UCS-4 encoding, any code point is encoded as 4- byte ( octet) binary numbers, while in the UTF-8 encoding, different code points are encoded as sequences from one to four bytes long, forming a self-synchronizing code.encode a particular code space in different ways, or.This is because one may wish to make these distinctions to: the abstract character from a particular graphical representation ( glyph).the number from an encoding as a sequence of bits, and.The notion of a code point is used for abstraction, to distinguish both: The Unicode code space is divided into seventeen planes (the basic multilingual plane, and 16 supplementary planes), each with 65,536 (= 2 16) code points. įor example, the character encoding scheme ASCII comprises 128 code points in the range 0 hex to 7F hex, Extended ASCII comprises 256 code points in the range 0 hex to FF hex, and Unicode comprises 1,114,112 code points in the range 0 hex to 10FFFF hex. The set of all possible code points within a given encoding/character set make up that encoding's codespace. Code points usually represent a single grapheme-usually a letter, digit, punctuation mark, or whitespace-but sometimes represent symbols, control characters, or formatting. In character encoding terminology, a code point, codepoint or code position is a numerical value that maps to a specific character. JSTOR ( March 2009) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.
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