<operating system> ("back up" when used as a verb) A spare
	copy of a file, file system, or other resource for use in the
	event of failure or loss of the original.

	The term commonly refers to a copy of the files on a
	computer's {disks}, made periodically and kept on {magnetic
	tape} or other removable medium (also called a "{dump}").

	This essential precaution is neglected by most new computer
	users until the first time they experience a {disk crash} or
	accidentally delete the only copy of the file they have been
	working on for the last six months.  Ideally the backup copies
	should be kept at a different site or in a fire safe since,
	though your hardware may be insured against fire, the data on
	it is almost certainly neither insured nor easily replaced.

	See also {backup software}, {differential backup},
	{incremental backup}, {full backup}.  Compare {archive},
	{source code management}.

	(2004-03-16)

1. <database> One or more large structured sets of persistent
	data, usually associated with software to update and {query}
	the data.  A simple database might be a single file containing
	many {records}, each of which contains the same set of
	{fields} where each field is a certain fixed width.

	A database is one component of a {database management system}.

	See also {ANSI/SPARC Architecture}, {atomic}, {blob}, {data
	definition language}, {deductive database}, {distributed
	database}, {fourth generation language}, {functional
	database}, {object-oriented database}, {relational database}.

	{Carol E. Brown's tutorial
	(http://accounting.rutgers.edu/raw/aies/www.bus.orst.edu/faculty/brownc/lectures/db_tutor/db_tutor.htm)}.

	2. <hypertext> A collection of {nodes} managed and stored in
	one place and all accessible via the same {server}.  {Links}
	outside this are "external", and those inside are "internal".

	On the {World-Wide Web} this is called a {website}.

	3. All the facts and rules comprising a {logic programming}
	program.

	(2005-11-17)

<operating system> 1. An undigested and voluminous mass of
	information about a problem or the state of a system,
	especially one routed to the slowest available output device
	(compare {core dump}), and most especially one consisting of
	{hexadecimal} or {octal} {runes} describing the byte-by-byte
	state of memory, mass storage, or some file.  In {elder days},
	debugging was generally done by "groveling over" a dump (see
	{grovel}); increasing use of high-level languages and
	interactive debuggers has made such tedium uncommon, and the
	term "dump" now has a faintly archaic flavour.

	2. A {backup}.  This usage is typical only at large
	{time-sharing} installations.

	{Unix manual page}: dump(1).

	[{Jargon File}]

	(1994-12-01)

<file system> An element of data storage in a {file system}.

	The history of computing is rich in varied kinds of files and
	{file systems}, whether ornate (e.g., {Macintosh file system}
	for a well-known case) or deficient (e.g., many simple
	pre-1980s file systems don't allow {directories}).

	However, the prototypical file has these characteristics:

	* It is a single sequence of bytes (but consider {Macintosh}
	{resource forks}).

	* It has a finite length, unlike, e.g. a {Unix} {device}.

	* It is stored in a {non-volatile storage} medium (but see
	{ramdrive}).

	* It exists (nominally) in a {directory}.

	* It has a name that it can be referred to by in file
	operations, possibly in combination with its {path}.

	Additionally, a file system may associate other information
	with a file, such as {permission} bits or other {file
	attributes}; timestamps for file creation, last revision, and
	last access; revision numbers (a` la VMS), and other kinds of
	{magic}.

	Compare: {document}.

	(1997-04-08)

1. (Originally {Unix}, now also {MS-DOS}) A program that
	processes an input data stream into an output data stream in
	some well-defined way, and does no I/O to anywhere else except
	possibly on error conditions; one designed to be used as a
	stage in a {pipeline} (see {plumbing}).  Compare {sponge}.

	2. ({functional programming}) A {higher-order function} which
	takes a {predicate} and a list and returns those elements of
	the list for which the predicate is true.  In {Haskell}:

		filter p []     = []
		filter p (x:xs) = if p x then x : rest else rest
				  where
				  rest = filter p xs

	See also {filter promotion}.

	[{Jargon File}]

1. <tool, language> (Named from the authors' initials) An
	interpreted language included with many versions of {Unix} for
	massaging text data, developed by Alfred Aho, Peter Weinberger,
	and Brian Kernighan in 1978.  It is characterised by {C}-like
	syntax, declaration-free variables, {associative arrays}, and
	field-oriented text processing.

	There is a {GNU} version called {gawk} and other varients
	including {bawk}, {mawk}, {nawk}, {tawk}.  {Perl} was inspired
	in part by awk but is much more powerful.

	{Unix manual page}: awk(1).

	{netlib WWW
	(http://plan9.att.com/netlib/research/index.html)}.  {netlib
	FTP (ftp://netlib.att.com/netlib/research/)}.

	["The AWK Programming Language" A. Aho, B. Kernighan,
	P. Weinberger, A-W 1988].

	2. <jargon> An expression which is awkward to manipulate
	through normal {regexp} facilities, for example, one
	containing a {newline}.

	[{Jargon File}]

	(1995-10-06)

1. <operating system> One of {Unix}'s buffers which can be
	written to by one {asynchronous} process and read by another,
	with the {kernel} suspending and waking up the sender and
	receiver according to how full the pipe is.  In later versions
	of Unix, rather than using an anonymous kernel-managed
	temporary file to implement a pipe, it can be named and is
	implemented as a local {socket} pair.

	2. <character> "|" {ASCII} character 124.  Used to represent a
	pipe between two processes in a {shell} command line.  E.g.

		grep foo log | more

	which feeds the output of grep into the input of more without
	requiring a named temporary file and without waiting for the
	first process to finish.

	3. <jargon, networking> A connection to a {network}.

	See also {light pipe}.

	(1996-09-24)

1. <programming, operating system> A simple item of data that
	identifies a resource.  For example, a {Unix} file handle
	identifies an open file and associated data such as whether it
	was opened for read or write and the current read/write
	position.  On the {Macintosh}, a handle is a pointer to a
	pointer to some dynamically-allocated memory.  The extra level
	of indirection allows on-the-fly {memory compaction} or
	{garbage collection} without invalidating application program
	references to the allocated memory.

	2. <jargon> An alias used intended to conceal a user's true
	identity in an electronic message.  The term is common on
	Citizen's Band and other amateur radio but, in that context
	usually means the user's real name as {FCC} rules forbid
	concealing one's identity.

	Use of grandiose handles is characteristic of {crackers},
	{weenies}, {spods}, and other lower forms of network life;
	true hackers travel on their own reputations.

	Compare {nick}.

	[{Jargon File}]

	(2004-07-20)