UTF-8

(redirected from Unicode (UTF-8))

UTF-8

(character)
(UCS transformation format 8) An ASCII-compatible multibyte Unicode and UCS encoding, used by Java and Plan 9.

The Unicode character set occupies a 16-bit code space. The most obvious Unicode encoding (known as UCS-2) consists of a sequence of 16-bit words. Such strings can contain bytes like '\0' or '/' which have a special meaning in filenames and other C library function parameters. In addition, the majority of Unix tools expects ASCII files and can't read 16-bit words as characters without major modifications. For these reasons, UCS-2 is not a suitable external encoding of Unicode in filenames, text files, environment variables, etc.

The ISO 10646 Universal Character Set (UCS), a superset of Unicode, occupies a 31-bit code space and the obvious UCS-4 encoding for it (a sequence of 32-bit words) has the same problems.

The UTF-8 encoding of Unicode and UCS avoids the problems of fixed-length Unicode encodings because an ASCII file encoded in UTF is exactly same as the original ASCII file and all non-ASCII characters are guaranteed to have the most significant bit set (bit 0x80). This means that normal tools for text searching etc. work as expected.

UTF-8 is defined in RFC 2279.

["File System Safe UCS Transformation Format (FSS_UTF)", X/Open Preliminary Specification, X/Open Company Ltd., Document Number: P316. This information also appears in ISO/IEC 10646, Annex P].

Plan 9 UTF manual entry.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

UTF-8

(Unicode Transformation Format-8) A format in the Unicode coding system that uses from one to four bytes. When coding the English language, only one byte is used per character like regular ASCII encoding. See Unicode and ASCII.
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.