UTF-1


UTF-1

UTF-1 is a way of transforming ISO 10646/Unicode into a stream of bytes. Due to the design it is not possible to resynchronise if decoding starts in the middle of a character (this makes truncation hard, among other things) and simple byte-oriented search routines cannot be reliably used with it. UTF-1 is also fairly slow due to its use of division. Due to these issues, UTF-1 never gained wide acceptance and has been almost totally replaced by UTF-8.

Design

UTF-1 is a multi-byte encoding like UTF-8, a single Unicode code point can be encoded in one, two, three, or five octets. While the ASCII range is encoded as one octet as in UTF-8 the ASCII octets 0x21 - 0x7E (decimal 33 - 126) are also used in UTF-1 multi-byte encodings, therefore UTF-1 is unsuited for many Internet protocols including MIME.

UTF-1 does not use the C0 and C1 control codes in other encodings, any 0x00 - 0x20 (decimal 0 - 32) and any 0x7F - 0x9F (decimal 127 - 159) octet stands for the corresponding code point u+0000 - u+0020 and u+007F - u+009F, respectively. This design with 66 "protected" octets tried to be ISO 2022 compatible.

The UTF-1 encoding scheme uses "modulo 190" arithmetics (256-66=190), it was designed to encode the complete 31 bits of the original Universal Character Set (UCS-4).For comparison, UTF-8 "protects" all 128 ASCII octets, and needs two bits in trail bytes of multi-byte encodings for this purpose, resulting in "modulo 64" (base 64) arithmetics (8-2=6, 2^6=64). BOCU-1 "protects" only the 13 octets 0x00, 0x07 - 0x0F, 0x1A - 0x1B, and 0x20 (space), covering the minimal set required for MIME-compatibility, resulting in "modulo 243" arithmetics (256-13=243).

See also

* Comparison of Unicode encodings
* Universal Character Set

References

* [http://www.itscj.ipsj.or.jp/ISO-IR/178.pdf ISO IR 178] (PDF, 256 KB, the retired UTF-1 specification)


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • UTF-8 — (8 bit Unicode Transformation Format) es un formato de codificación de caracteres Unicode e ISO 10646 utilizando símbolos de longitud variable. UTF 8 fue creado por Robert C. Pike y Kenneth L. Thompson. Está definido como estándar por la RFC 3629 …   Wikipedia Español

  • UTF-7 — (7 bit Unicode Transformation Format) is a variable length character encoding that was proposed for representing Unicode text using a stream of ASCII characters. It was originally intended to provide a means of encoding Unicode text for use in… …   Wikipedia

  • UTF-8 — (от англ. Unicode Transformation Format, 8 bit  «формат преобразования Юникода, 8 битный»)  распространённая кодировка символов Юникода, совместимая с 8 битными форматами передачи текста. Нашла широкое применение в операционных… …   Википедия

  • UTF-8 — (Abk. für 8 bit UCS Transformation Format wobei UCS wiederum Universal Character Set abkürzt) ist die am weitesten verbreitete Kodierung für Unicode Zeichen (Unicode und UCS sind praktisch identisch). Die Kodierung wurde im September 1992 von Ken …   Deutsch Wikipedia

  • UTF-7 — (7 bit Unicode Transformation Format) es una codificación de caracteres de longitud variable que fue propuesta para representar texto codificado con Unicode usando un flujo de caracteres ASCII, para ser usado, por ejemplo en mensajes de correo… …   Wikipedia Español

  • UTF-8 — (UCS Transformation Format  8 bit[1]) is a multibyte character encoding for Unicode. Like UTF 16 and UTF 32, UTF 8 can represent every character in the Unicode character set. Unlike them, it is backward compatible with ASCII and avoids the… …   Wikipedia

  • UTF-16 — (англ. Unicode Transformation Format) в информатике один из способов кодирования символов из Unicode в виде последовательности 16 битных слов. Данная кодировка позволяет записывать символы Юникода в диапазонах U+0000..U+D7FF и… …   Википедия

  • UTF-16 — est un codage des caractères définis par Unicode où chaque caractère est codé sur une suite de un ou deux mots de 16 bits. Le codage était défini dans le rapport technique 17 à la norme Unicode. Depuis, cette annexe est devenue obsolète car UTF… …   Wikipédia en Français

  • Utf-16 — Unicode Jeux de caractères UCS (ISO/CEI 10646) ISO 646, ASCII ISO 8859 1 WGL4 UniHan Équivalences normalisées NFC (précomposée) NFD (décomposée) NFKC (compatibilité) NFKD (compatibilité) Propriétés et algorithmes ISO 15924 …   Wikipédia en Français

  • Utf-8 — (от англ. Unicode Transformation Format формат преобразования Юникода) в настоящее время распространённая кодировка, реализующая представление Юникода, совместимое с 8 битным кодированием текста. Текст, состоящий только из символов с номером… …   Википедия

  • UTF-8 — (UCS transformation format 8 bits) est un format de codage de caractères. Chaque caractère ou graphème est représenté dans le répertoire du jeu universel de caractères sous la forme d’une suite d’un ou plusieurs « caractères abstraits » …   Wikipédia en Français


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.