Specials (Unicode block)

{{short description|Unicode block containing some special codepoints and two non-characters}}

{{Infobox Unicode block

|blockname = Specials

|rangestart = FFF0

|rangeend = FFFF

|script1 = Common

|1_0_0 = 1

|2_1 = 1

|3_0 = 3

|nonchar = 2

|note = {{Cite web|url=https://www.unicode.org/ucd/|title=Unicode character database|work=The Unicode Standard|access-date=2023-07-26}}{{Cite web|url=https://www.unicode.org/versions/enumeratedversions.html|title=Enumerated Versions of The Unicode Standard|work=The Unicode Standard|access-date=2023-07-26}}

}}

Specials is a short Unicode block of characters allocated at the very end of the Basic Multilingual Plane, at U+FFF0–FFFF, containing these code points:

• {{unichar|FFF9|INTERLINEAR ANNOTATION ANCHOR}}, marks start of annotated text
• {{unichar|FFFA|INTERLINEAR ANNOTATION SEPARATOR}}, marks start of annotating character(s)
• {{unichar|FFFB|INTERLINEAR ANNOTATION TERMINATOR}}, marks end of annotation block
• {{unichar|FFFC|OBJECT REPLACEMENT CHARACTER}}, placeholder in the text for another unspecified object, for example in a compound document.
• {{unichar|FFFD|REPLACEMENT CHARACTER}} used to replace an unknown, unrecognised, or unrepresentable character
• {{unichar|FFFE|}} not a character.
• {{unichar|FFFF|}} not a character.

{{unichar|FFFE|}} and {{unichar|FFFF|}} are noncharacters, meaning they are reserved but do not cause ill-formed Unicode text. Versions of the Unicode standard from 3.1.0 to 6.3.0 claimed that these characters should never be interchanged, leading some applications to use them to guess text encoding by interpreting the presence of either as a sign that the text is not Unicode. However, Corrigendum #9 later specified that noncharacters are not illegal and so this method of checking text encoding is incorrect.{{cite web|url=http://www.unicode.org/versions/corrigendum9.html|title=Corrigendum #9: Clarification About Noncharacters|work=The Unicode Standard|access-date=2023-06-07|url-status=live |archive-url=https://web.archive.org/web/20230610160203/http://www.unicode.org/versions/corrigendum9.html |archive-date=Jun 10, 2023}} An example of an internal usage of U+FFFE is the CLDR algorithm; this extended Unicode algorithm maps the noncharacter to a minimal, unique primary weight.{{cite web|url=http://www.unicode.org/reports/tr35/tr35-collation.html#Algorithm_FFFE|title=Unicode Technical Standard #35|work=Unicode Locale Data Markup Language (LDML)|access-date=2024-08-27}}

Unicode's {{unichar|FEFF|Byte order mark}} character can be inserted at the beginning of a Unicode text to signal its endianness: a program reading such a text and encountering 0xFFFE would then know that it should switch the byte order for all the following characters.

Its block name in Unicode 1.0 was Special.{{cite web |url=https://www.unicode.org/versions/Unicode1.0.0/CodeCharts2.pdf |work=The Unicode Standard |version=Version 1.0 |title=3.8: Block-by-Block Charts |publisher=Unicode Consortium |access-date=2020-09-30 |archive-date=2021-02-11 |archive-url=https://web.archive.org/web/20210211080017/https://www.unicode.org/versions/Unicode1.0.0/CodeCharts2.pdf |url-status=live }}