Text of ISO 10646 – AMD 18 for PDAM registration and FPDAM ballot, Īliprand, 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 (), "7.3", Unconfirmed Meeting Minutes, WG 2 Meeting # 33, Heraklion, Crete, Greece, 20 June – 4 July 1997 Ksar, Mike (), "8.14", Draft minutes of WG2 Copenhagen Meeting # 30
Sargent, Murray (), Proposal Summary – Object Replacement Character Sargent, Murray (), Recommendation to encode a WCH_EMBEDDING characterĪliprand, Joan Hart, Edwin Greenfield, Steve (), "Embedded Objects", UTC #67 Minutes (), "9.3 Allowing FFFF and FFFE in UTF-8", Draft minutes of WG 2 meeting 41, Hotel Phoenix, Singapore, /19 Moore, Lisa (), "Motion 88-M2", Minutes from the UTC/L2 meeting #88ĭavis, Mark (), Request to allow FFFF, FFFE in UTF-8 in the text of ISO/IEC 10646 The following Unicode-related documents record the purpose and process of defining specific characters in the Specials block:
^ Black areas indicate noncharacters (code points that are guaranteed never to be assigned as encoded characters in the Unicode Standard)
^ Grey areas indicate non-assigned code points 3. Official Unicode Consortium code chart (PDF)
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. Thus the replacement character is now only seen for encoding errors, such as invalid UTF-8. There is no Unicode code point for this symbol. notdef character, which in most cases is an empty box (or "?" or "X" in a box ), sometimes called a " tofu" (this browser displays ?). However most modern text rendering systems instead use a font's.
This will allow the text editor to save the original byte sequence, while still showing the error indicator to the user.Īt one time the replacement character was often used when there was no glyph available in a font for that 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. Since the replacement is the same for all errors this makes it impossible to recover the original character. The whole string now displays like this: "f�r".Ī poorly implemented text editor might save the replacement in UTF-8 form the text file data will then look like this: 0圆6 0圎F 0xBF 0xBD 0x72, which will be displayed in ISO-8859-1 as "f�r" (this is called mojibake). Therefore, a text editor could replace this byte with the replacement character symbol to produce a valid string of Unicode code points. 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. This file is now opened with a text editor that assumes the input is UTF-8. It is usually seen when the data is invalid and does not match any character:Ĭonsider a text file containing the German word für (meaning 'for') in the ISO-8859-1 encoding ( 0圆6 0xFC 0x72). It is used to indicate problems when a system is unable to render a stream of data to a correct symbol. The replacement character � (often displayed as a black rhombus with a white question mark) is a symbol found in the Unicode standard at code point U+FFFD in the Specials table. Its block name in Unicode 1.0 was Special. Unicode's U+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. 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. U+FFFD � REPLACEMENT CHARACTER used to replace an unknown, unrecognized, or unrepresentable characterįFFE and FFFF are not unassigned in the usual sense, but guaranteed not to be Unicode characters at all.U+FFFC  OBJECT REPLACEMENT CHARACTER, placeholder in the text for another unspecified object, for example in a compound document.U+FFFB INTERLINEAR ANNOTATION TERMINATOR, marks end of annotation block.U+FFFA INTERLINEAR ANNOTATION SEPARATOR, marks start of annotating character(s).U+FFF9 INTERLINEAR ANNOTATION ANCHOR, marks start of annotated text.Of these 16 code points, five have been assigned since Unicode 3.0: Specials is a short Unicode block of characters allocated at the very end of the Basic Multilingual Plane, at U+FFF0–FFFF.