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UTC

UTF

UTF-8

(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.

Last updated: 1998-07-29

utility

utility software

utility-coder

<language>

A language for data manipulation and report generation.

["User's Manual for utility-coder", Cambridge Computer Association, Jul 1977].

Last updated: 1997-12-09

utility program

utility software

<tool>

(Or utility program, tool) Any software that performs some specific task that is secondary to the main purpose of using the computer (the latter would be called application programs) but is not essential to the operation of the computer (system software).

Many utilities could be considered as part of the system software, which can in turn be considered part of the operating system.

The following are some broad categories of utility software, specific types and examples.

* Disks

disk formatter: FDISK, format

backup

file system compression

* Files and directories

list directory: ls, dir