<programming> (Or "released version", "baseline") A version of
	a piece of software which has been made public (as opposed to
	a version that is in development, or otherwise unreleased).

	A release is either a {major release}, a {revision}, or a
	{bugfix}.

	Pre-release versions may be called {alpha test}, or {beta
	test} versions.

	See {change management}.

	(1996-08-04)

<programming, library> A collection of {subroutines} and
	{functions} stored in one or more files, usually in compiled
	form, for linking with other programs.  Libraries are one of
	the earliest forms of organised {code reuse}.  They are often
	supplied by the {operating system} or {software development
	environment} developer to be used in many different programs.
	The routines in a library may be general purpose or designed
	for some specific function such as three dimensional animated
	graphics.

	Libraries are linked with the user's program to form a
	complete {executable}.  The linking may be {static linking}
	or, in some systems, {dynamic linking}.

	(1998-11-21)

1. <mathematics> One instance of some mathematical object
	contained with in another instance, e.g. a {group} which is a
	subgroup.

	2. <theory> ({domain theory}) A {complete partial order} F in
	[X -> Y] is an embedding if

	(1) For all x1, x2 in X, x1 <= x2  <=>  F x1 <= F x2 and

	(2) For all y in Y, {x | F x <= y} is {directed}.

	("<=" is written in {LaTeX} as {\sqsubseteq}).

	(1995-03-27)

(FTP) A {client-server} protocol which allows a user on one
	computer to transfer files to and from another computer over a
	{TCP/IP} network.  Also the client program the user executes
	to transfer files.  It is defined in {STD 9}, {RFC 959}.

	See also {anonymous FTP}, {FSP}, {TFTP}.

	{Unix manual page}: ftp(1).

	(1994-12-01)

After-sale handholding; something many software vendors
	promise but few deliver.  To hackers, most support people are
	useless - because by the time a hacker calls support he or she
	will usually know the software and the relevant manuals better
	than the support people (sadly, this is *not* a joke or
	exaggeration).  A hacker's idea of "support" is a tte--tte
	or exchange of {electronic mail} with the software's designer.

	[{Jargon File}]

	(1995-02-15)

1. <data, graphics> Data representing a two-dimensional scene.
	A digital image is composed of {pixels} arranged in a
	rectangular array with a certain height and width.  Each pixel
	may consist of one or more {bits} of information, representing
	the brightness of the image at that point and possibly
	including colour information encoded as {RGB} triples.

	{Images} are usually taken from the real world via a {digital
	camera}, {frame grabber}, or {scanner}; or they may be
	generated by computer, e.g. by {ray tracing} software.

	See also {image formats}, {image processing}.

	(1994-10-21)

	2. <mathematics> The image (or range) of a {function} is the
	set of values obtained by applying the function to all
	elements of its {domain}.  So, if f : D -> C then the set f(D)
	= \{ f(d) | d in D \} is the image of D under f.  The image is
	a subset of C, the {codomain}.

	(2000-01-19)

<language, programming> (Or "source", or rarely "source
	language") The form in which a computer program is written by
	the programmer.  Source code is written in some formal
	programming language which can be compiled automatically into
	{object code} or {machine code} or executed by an
	{interpreter}.

	(1995-01-05)

<programming> The name given in {Smalltalk} and other
	{object-oriented languages} to a procedure or routine
	associated with one or more {classes}.  An {object} of a
	certain class knows how to perform actions, e.g. printing
	itself or creating a new instance of itself, rather than the
	function (e.g. printing) knowing how to handle different types
	of object.

	Different classes may define methods with the same name
	(i.e. methods may be {polymorphic}).  The term "method" is used
	both for a named operation, e.g. "PRINT" and also for the code
	which a specific class provides to perform tha
	t operation.

	Most methods operate on objects that are instances of a
	certain class.  Some object-oriented languages call these
	"object methods" to distinguish then from "{class methods}".

	In {Smalltalk}, a method is defined by giving its name,
	documentation, temporary local variables and a sequence of
	expressions separated by "."s.

	(2000-03-22)

<programming> A special value used in several languages to
	represent the thing referred to by an uninitialised pointer.

	<database> A special value that may be stored in some database
	columns to represent an unknown, missing, not applicable, or
	undefined value.  Nulls are treated completely differently
	from ordinary values when evaluating SQL expressions and there
	are several SQL constructs for dealing with nulls.

	(2003-06-17)

1. A program which provides some service to other ({client})
	programs.  The connection between client and server is
	normally by means of {message passing}, often over a
	{network}, and uses some {protocol} to encode the client's
	requests and the server's responses.  The server may run
	continuously (as a {daemon}), waiting for requests to arrive
	or it may be invoked by some higher level daemon which
	controls a number of specific servers ({inetd} on {Unix}).

	There are many servers associated with the {Internet}, such as
	those for {HTTP}, {Network File System}, {Network Information
	Service} (NIS), {Domain Name System} (DNS), {FTP}, {news},
	{finger}, {Network Time Protocol}.  On Unix, a long list can
	be found in /etc/services or in the {NIS} database "services".
	See {client-server}.

	2. A computer which provides some service for other computers
	connected to it via a network.  The most common example is a
	{file server} which has a local disk and services requests
	from remote clients to read and write files on that disk,
	often using {Sun}'s {Network File System} (NFS) {protocol} or
	{Novell Netware} on {PCs}.  Another common example is a {web
	server}.

	[{Jargon File}]

	(2003-12-29)

1. To wait for an event that will never occur.  "The system is
	hanging because it can't read from the crashed drive".  See
	{wedged}, {hung}.

	2. To wait for some event to occur; to hang around until
	something happens.  "The program displays a menu and then
	hangs until you type a character."  Compare {block}.

	3. To attach a peripheral device, especially in the
	construction "hang off": "We're going to hang another tape
	drive off the file server."  Implies a device attached with
	cables, rather than something that is strictly inside the
	machine's chassis.

A period of time after which an error condition is raised if
	some event has not occured.  A common example is sending a
	message.  If the receiver does not acknowledge the message
	within some preset timeout period, a transmission error is
	assumed to have occured.

	(1995-11-09)

<character> An {atom} in a {character repertoire}.

	Compare with {glyph}.

	(1998-10-18)

<file system> A node in a hierarchical {file system} which
	contains zero or more other nodes - generally, {files} or
	other directories.

	Compare {folder}.

	(1997-04-10)

<programming> An unwanted and unintended property of a program
	or piece of hardware, especially one that causes it to
	malfunction.  Antonym of {feature}.  E.g. "There's a bug in
	the editor: it writes things out backward."  The
	identification and removal of bugs in a program is called
	"{debugging}".

	Admiral {Grace Hopper} (an early computing pioneer better
	known for inventing {COBOL}) liked to tell a story in which a
	technician solved a {glitch} in the {Harvard Mark II machine}
	by pulling an actual insect out from between the contacts of
	one of its relays, and she subsequently promulgated {bug} in
	its hackish sense as a joke about the incident (though, as she
	was careful to admit, she was not there when it happened).
	For many years the logbook associated with the incident and
	the actual bug in question (a moth) sat in a display case at
	the Naval Surface Warfare Center (NSWC).  The entire story,
	with a picture of the logbook and the moth taped into it, is
	recorded in the "Annals of the History of Computing", Vol. 3,
	No. 3 (July 1981), pp. 285--286.

	The text of the log entry (from September 9, 1947), reads
	"1545 Relay #70 Panel F (moth) in relay.  First actual case of
	bug being found".  This wording establishes that the term was
	already in use at the time in its current specific sense - and
	Hopper herself reports that the term "bug" was regularly
	applied to problems in radar electronics during WWII.

	Indeed, the use of "bug" to mean an industrial defect was
	already established in Thomas Edison's time, and a more
	specific and rather modern use can be found in an electrical
	handbook from 1896 ("Hawkin's New Catechism of Electricity",
	Theo. Audel & Co.)  which says: "The term "bug" is used to a
	limited extent to designate any fault or trouble in the
	connections or working of electric apparatus."  It further
	notes that the term is "said to have originated in
	{quadruplex} telegraphy and have been transferred to all
	electric apparatus."

	The latter observation may explain a common folk etymology of
	the term; that it came from telephone company usage, in which
	"bugs in a telephone cable" were blamed for noisy lines.
	Though this derivation seems to be mistaken, it may well be a
	distorted memory of a joke first current among *telegraph*
	operators more than a century ago!

	Actually, use of "bug" in the general sense of a disruptive
	event goes back to Shakespeare!  In the first edition of
	Samuel Johnson's dictionary one meaning of "bug" is "A
	frightful object; a walking spectre"; this is traced to
	"bugbear", a Welsh term for a variety of mythological monster
	which (to complete the circle) has recently been reintroduced
	into the popular lexicon through fantasy {role-playing games}.

	In any case, in jargon the word almost never refers to
	insects.  Here is a plausible conversation that never actually
	happened:

	"There is a bug in this ant farm!"

	"What do you mean?  I don't see any ants in it."

	"That's the bug."

	[There has been a widespread myth that the original bug was
	moved to the Smithsonian, and an earlier version of this entry
	so asserted.  A correspondent who thought to check discovered
	that the bug was not there.  While investigating this in late
	1990, your editor discovered that the NSWC still had the bug,
	but had unsuccessfully tried to get the Smithsonian to accept
	it - and that the present curator of their History of
	American Technology Museum didn't know this and agreed that it
	would make a worthwhile exhibit.  It was moved to the
	Smithsonian in mid-1991, but due to space and money
	constraints has not yet been exhibited.  Thus, the process of
	investigating the original-computer-bug bug fixed it in an
	entirely unexpected way, by making the myth true!  - ESR]

	[{Jargon File}]

	(1999-06-29)

1. A discrepancy between a computed, observed, or measured
	value or condition and the true, specified, or theoretically
	correct value or condition.

	2. <programming> A mental mistake made by a programmer that
	may result in a program {fault}.

	3. (verb) What a program does when it stops as result of a
	programming error.

	(2000-03-28)

<data, data processing, jargon> /day't*/ (Or "raw data")
	Numbers, {characters}, {images}, or other method of recording,
	in a form which can be assessed by a human or (especially)
	input into a {computer}, stored and {processed} there, or
	transmitted on some {digital channel}.  Computers nearly
	always represent data in {binary}.

	Data on its own has no meaning, only when interpreted by some
	kind of {data processing system} does it take on meaning and
	become {information}.

	People or computers can find patterns in data to perceive
	information, and information can be used to enhance
	{knowledge}.  Since knowledge is prerequisite to wisdom, we
	always want more data and information.  But, as modern
	societies verge on {information overload}, we especially need
	better ways to find patterns.

	1234567.89 is data.

	"Your bank balance has jumped 8087% to $1234567.89" is
	information.

	"Nobody owes me that much money" is knowledge.

	"I'd better talk to the bank before I spend it, because of
	what has happened to other people" is wisdom.

	(1999-04-30)

<body> A business, generally a large one.

	(1994-11-22)

<programming> One of a sequence of copies of a program, each
	incorporating new modifications.  Each version is usually
	identified by a number, commonly of the form X.Y where X is
	the major version number and Y is the release number.
	Typically an increment in X (with Y reset to zero) signifies a
	substantial increase in the function of the program or a
	partial or total re-implementation, whereas Y increases each
	time the progam is changed in any way and re-released.

	Version numbers are useful so that the user can know if the
	program has changed ({bugs} have been fixed or new functions
	added) since he obtained his copy and the programmer can tell
	if a bug report relates to the current version.  It is thus
	always important to state the version when reporting bugs.
	Statements about compatibility between different software
	components should always say which versions they apply to.

	See {change management}.

	(1997-12-07)