Specials (Unicode block)

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: U+FFF9 INTERLINEAR ANNOTATION ANCHOR, marks start of annotated text U+FFFA INTERLINEAR ANNOTATION SEPARATOR, marks start of annotating character(s) U+FFFB INTERLINEAR ANNOTATION TERMINATOR, marks end of annotation block U+FFFC  OBJECT REPLACEMENT CHARACTER, placeholder in the text for another unspecified object, for example in a compound document. U+FFFD � REPLACEMENT CHARACTER used to replace an unknown, unrecognised, or unrepresentable character U+FFFE <noncharacter-FFFE> not a character. U+FFFF <noncharacter-FFFF> not a character. U+FFFE <noncharacter-FFFE> and U+FFFF <noncharacter-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. 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. Unicode's U+FEFF ZERO WIDTH NO-BREAK SPACE character can be inserted at the beginning of a Unicode text as a byte order mark to signal its endianness: a program reading a text encoded in for example UTF-16 and encountering U+FFFE <noncharacter-FFFE> would then know that it should switch the byte order for all the following characters. Its block name in Unicode 1.0 was Special.