Specials (Unicode block)
（重定向自Replacement character）
Specials is the name of a short Unicode block allocated at the very end of the Basic Multilingual Plane, at U+FFF0–FFFF. Of these 16 codepoints, five are assigned as of Unicode 8.0:
FFFE and FFFF are not unassigned in the usual sense, but guaranteed not to be a Unicode character at all. They can be used to guess a text's encoding scheme, since any text containing these is by definition not a correctly encoded Unicode text. Unicode's U+FEFFBYTE 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.