Unicode block: Difference between revisions

Revision as of 18:53, 25 August 2023

Revision as of 19:21, 25 August 2023

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{{Short description|Named range of Unicode code points}}

<ref name=":2" />A<ref>{{Cite web |title= |url=}}</ref><ref name=":2">{{Cite news |title=}}</ref><ref name=":1">{{Cite book |title=}}</ref><ref name=":0" /> '''Unicode block''' is one of several contiguous ranges of numeric character codes ([[code point]]s) of the [[Unicode]] character set that are defined by the [[Unicode Consortium]] for administrative and documentation purposes. Typically, proposals such as the addition of new glyphs are discussed and evaluated by considering the relevant block or blocks as a whole.<ref name="uniblocks" />

Each block is generally, but not always, meant to supply glyphs used by one or more specific languages, or in some general application area such as [[mathematics]], [[surveying]], decorative [[typesetting]], social forums, etc.

== <ref name=":1" />Design and implementation ==

Unicode blocks are identified by unique names, which use only ASCII characters and are usually descriptive of the nature of the symbols, in [[English language|English]]; such as "Tibetan" or "Supplemental Arrows-A". (When comparing block names, one is supposed to equate uppercase with lowercase letters, and ignore any whitespace, hyphens, and underbars; so the last name is equivalent to "supplemental_arrows__a" and "SUPPLEMENTALARROWSA".<ref name=uniblocks>{{Cite web|url=https://www.unicode.org/Public/UNIDATA/Blocks.txt|title=Unicode Blocks data file, Unicode version 14.0|publisher=Unicode Consortium|access-date=2021-09-15}}</ref>

Blocks are [[intersection (set theory)|pairwise disjoint]]; that is, they do not overlap. The starting code point and the size (number of code points) of each block are always multiples of 16; therefore, in the [[hexadecimal notation]], the starting (smallest) point is U+''xxx''0 and the ending (largest) point is U+''yyy''F, where ''xxx'' and ''yyy'' are three or more hexadecimal digits. (These constraints are intended to simplify the display of glyphs in Unicode Consortium documents, as tables with 16 columns labeled with the last hexadecimal digit of the code point.<ref name=uniblocks/>) The size of a block may range from the minimum of 16 to a maximum of 65,536 code points.

Every assigned code point has a glyph property called "Block", whose value is a character string naming the unique block that owns that point.<ref>{{Cite web |title=Glossary |url=https://www.unicode.org/glossary/#B |access-date=2022-08-07 |website=www.unicode.org}}</ref> However, a block may also contain unassigned code points, usually reserved for future additions of characters that "logically" should belong to that block. Code points not belonging to any of the named blocks, e.g. in the unassigned [[Plane (Unicode)|planes]] 4–13, have the value block="No_Block".<ref name=uniblocks/>

Simply belonging to a particular Unicode block does not guarantee the certain particular properties of the characters it is or will be expected to contain. The identity of any character is determined by its properties stated in the Unicode Character Database. For example, the contiguous range of 32 noncharacter code points U+FDD0..U+FDEF share none of the properties common to the other characters in the [[Arabic Presentation Forms-A]] block, that they are certainly not Arabic script characters or "right-to-left noncharacters", and are assigned there as a filler to this block given that it has been agreed that no further Arabic compatibility characters will be encoded. <ref name=":0">{{Cite web |title=Private-Use Characters, Noncharacters & Sentinels FAQ |url=https://www.unicode.org/faq/private_use.html |access-date=2023-07-24 | website=www.unicode.org}}</ref>

== Other classifications ==