(16 code points)
|Assigned||5 code points|
|Unused||9 reserved code points |
|Unicode version history|
FFFE and FFFF are not unassigned in the usual sense, but guaranteed not to be Unicode characters 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 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.
The replacement character ? (often displayed as a black diamond with a white question mark) is a symbol found in the Unicode standard at code point U+FFFD in the Specials table. It is used to indicate problems when a system is unable to render a stream of data to a correct symbol. It is usually seen when the data is invalid and does not match any character:
Consider a text file containing the German word für (meaning 'for') in the ISO-8859-1 encoding (
0x66 0xFC 0x72). This file is now opened with a text editor that assumes the input is UTF-8. The first and last byte are valid UTF-8 encodings of ASCII, but the middle byte (
0xFC) is not a valid byte in UTF-8. Therefore, a text editor could replace this byte with the replacement character symbol to produce a valid string of Unicode code points. The whole string now displays like this: "f?r".
A poorly implemented text editor might save the replacement in UTF-8 form; the text file data will then look like this:
0x66 0xEF 0xBF 0xBD 0x72, which will be displayed in ISO-8859-1 as "fï¿½r" (this is called mojibake). Since the replacement is the same for all errors this makes it impossible to recover the original character. A better (but harder to implement) design is to preserve the original bytes, including the error, and only convert to the replacement when displaying the text. This will allow the text editor to save the original byte sequence, while still showing the error indicator to the user.
At one time the replacement character was often used when there was no glyph available in a font for that character. However most modern text rendering systems instead use a font's .notdef character, which in most cases is an empty box (or "?" or "X" in a box), sometimes called a "tofu" (this browser displays ). There is no Unicode code point for this symbol.
Thus the replacement character is now only seen for encoding errors, such as invalid UTF-8. Some software attempts to hide this by translating the bytes of invalid UTF-8 to matching characters in Windows-1252 (since that is the most likely source of these errors), so that the replacement character is never seen.
Official Unicode Consortium code chart (PDF)
The following Unicode-related documents record the purpose and process of defining specific characters in the Specials block:
|Version||Count||UTC ID||L2 ID||WG2 ID||Document|
|1.0.0||U+FFFD||1||(to be determined)|
|U+FFFE..FFFF||2||(to be determined)|
|Moore, Lisa (2001-11-06), "Motion 88-M2", Minutes from the UTC/L2 meeting #88|
|doc)||Davis, Mark (2001-09-26), Request to allow FFFF, FFFE in UTF-8 in the text of ISO/IEC 10646|
|N2403||Umamaheswaran, V. S. (2002-04-22), "9.3 Allowing FFFF and FFFE in UTF-8", Draft minutes of WG 2 meeting 41, Hotel Phoenix, Singapore, 2001-10-15/19|
|2.1||U+FFFC||1||Sargent, Murray (1995-12-06), Recommendation to encode a WCH_EMBEDDING character|
|Aliprand, Joan; Hart, Edwin; Greenfield, Steve (1996-03-05), "Embedded Objects", UTC #67 Minutes|
|N1365||Sargent, Murray (1996-03-18), Proposal Summary - Object Replacement Character|
|N1353||Umamaheswaran, V. S.; Ksar, Mike (1996-06-25), "8.14", Draft minutes of WG2 Copenhagen Meeting # 30|
|N1603||Umamaheswaran, V. S. (1997-10-24), "7.3", Unconfirmed Meeting Minutes, WG 2 Meeting # 33, Heraklion, Crete, Greece, 20 June - 4 July 1997|
|N1681||Text of ISO 10646 - AMD 18 for PDAM registration and FPDAM ballot, 1997-12-22|
|Aliprand, Joan; Winkler, Arnold, "Additional comments regarding 2.1", Minutes of the joint UTC and L2 meeting from the meeting in Cupertino, February 25-27, 1998|
|N1894||Revised text of 10646-1/FPDAM 18, AMENDMENT 18: Symbols and Others, 1998-10-22|
|3.0||U+FFF9..FFFB||3||Aliprand, Joan (1997-12-03), "3.D Proposal for In-Line Notation (ruby)", Approved Minutes - UTC #73 & L2 #170 joint meeting, Palo Alto, CA - August 4-5, 1997|
|Freytag, Asmus (1998-02-22), Support for Implementing Inline and Interlinear Annotations|
|Aliprand, Joan; Winkler, Arnold, "3.C.5. Support for implementing inline and interlinear annotations", Minutes of the joint UTC and L2 meeting from the meeting in Cupertino, February 25-27, 1998|
|N1727||Freytag, Asmus (1998-03-18), Support for Implementing Interlinear Annotations as used in East Asian Typography|
|Aliprand, Joan; Winkler, Arnold (1998-05-26), "Inline and Interlinear Annotations", Draft Minutes - UTC #76 & NCITS Subgroup L2 #173 joint meeting, Tredyffrin, Pennsylvania, April 20-22, 1998|
|N1703||Umamaheswaran, V. S.; Ksar, Mike (1998-07-02), "8.14", Unconfirmed Meeting Minutes, WG 2 Meeting #34, Redmond, WA, USA; 1998-03-16--20|
|Hiura, Hideki; Kobayashi, Tatsuo (1998-07-29), Suggestion to the inline and interlinear annotation proposal|
|html)||Aliprand, Joan (1998-07-31), "In-Line and Interlinear Annotation (III.C.1.c)", Unconfirmed Minutes - UTC #77 & NCITS Subgroup L2 # 174 JOINT MEETING, Redmond, WA -- July 29-31, 1998|
|N1861||Sato, T. K. (1998-09-01), Ruby markers|
|doc)||Whistler, Ken; et al. (1998-09-22), Additional Characters for the UCS|
|Support for Implementing Interlinear Annotations, 1998-09-23|
|N1920||Combined PDAM registration and consideration ballot on WD for ISO/IEC 10646-1/Amd. 30, AMENDMENT 30: Additional Latin and other characters, 1998-10-28|
|Suignard, Michel; Hiura, Hideki (1998-12-04), Notes concerning the PDAM 30 interlinear annotation characters|
|html, doc)||Umamaheswaran, V. S. (1998-12-30), "8.2.15", Minutes of WG 2 meeting 35, London, U.K.; 1998-09-21--25|
|doc)||Aliprand, Joan (1999-02-05), "Interlinear Annotation Characters", Approved Minutes -- UTC #78 & NCITS Subgroup L2 # 175 Joint Meeting, San Jose, CA -- December 1-4, 1998|
|Duerst, Martin; Bosak, Jon (1999-06-08), W3C XML CG statement on annotation characters|
|Moore, Lisa (1999-11-04), "W3C Liaison Statement on Annotation Characters", Minutes from the joint UTC/L2 meeting in Seattle, June 8-10, 1999|
|Whistler, Ken (2001-08-01), "E. Indicated as "strongly discouraged" for plain text interchange", Analysis of Character Deprecation in the Unicode Standard|