1. A sudden, usually drastic failure.  Most often said of the
	{system}, especially of magnetic disk drives (the term
	originally described what happened when the air gap of a hard
	disk collapses).  "Three {lusers} lost their files in last
	night's disk crash."  A disk crash that involves the
	read/write heads dropping onto the surface of the disks and
	scraping off the oxide may also be referred to as a "head
	crash", whereas the term "system crash" usually, though not
	always, implies that the operating system or other software
	was at fault.

	2. To fail suddenly.  "Has the system just crashed?"
	"Something crashed the OS!" See {down}.  Also used
	transitively to indicate the cause of the crash (usually a
	person or a program, or both).  "Those idiots playing
	{SPACEWAR} crashed the system."

	[{Jargon File}]

	(1994-12-01)

1. <programming> An {address}, from the point of view of a
	programming language.  A pointer may be typed, with its {type}
	indicating the type of data to which it points.

	The terms "pointer" and "reference" are generally
	interchangable although particular programming languages often
	differentiate these two in subtle ways.  For example, {Perl}
	always calls them references, never pointers.  Conversely, in
	C, "pointer" is used, although "a reference" is often used to
	denote the concept that a pointer implements.

	{Anthony Hoare} once said:

	Pointers are like jumps, leading wildly from one part of the
	data structure to another.  Their introduction into high-level
	languages has been a step backward from which we may never
	recover.

	[C.A.R.Hoare "Hints on Programming Language Design", 1973,
	Prentice-Hall collection of essays and papers by Tony Hoare].

	2. <operating system> (Or "mouse pointer") An {icon}, usually
	a small arrow, that moves on the screen in response to
	movement of a {pointing device}, typically a {mouse}.  The
	pointer shows the user which object on the screen will be
	selected etc. when a mouse button is clicked.

	(1999-07-07)

<object-oriented> In {object-oriented programming}, an
	instance of the data structure and behaviour defined by the
	object's {class}.  Each object has its own values for the
	{instance variables} of its class and can respond to the
	{methods} defined by its class.

	For example, an object of the "Point" class might have
	instance variables "x" and "y" and might respond to the "plot"
	method by drawing a dot on the screen at those coordinates.

	(2004-01-26)

In {object-oriented programming} sending a message to an
	{object} (to invoke a {method}) is equivalent to calling a
	{procedure} in traditional programming languages, except that
	the actual code executed may only be selected at run time
	depending on the {class} of the object.  Thus, in response to
	the message "drawSelf", the method code invoked would be
	different if the target object were a circle or a square.

	(1995-02-16)

A language proposed by Cii {Honeywell-Bull} to meet the DoD
	{Ironman} requirements which led to {Ada}.  This language won
	in 1979.

	["On the GREEN Language Submitted to the DoD", E.W. Dijkstra,
	SIGPLAN Notices 13(10):16-21 (Oct 1978)].

	(1994-12-02)

(From Zen Buddhist koans of the form "Does an X have the
	Buddha-nature?") Common hacker construction for "is an X",
	used for humorous emphasis.  "Anyone who can't even use a
	program with on-screen help embedded in it truly has the
	{loser} nature!"  See also {the X that can be Y is not the
	true X}.

	[{Jargon File}]

	(1995-01-11)

See also {complete graph}, {complete inference system},
	{complete lattice}, {complete metric space}, {complete partial
	ordering}, {complete theory}.

	[1. or 2. or both?]

	(1996-04-24)

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)

<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)

1. Not simulated.  Often used as a specific antonym to
	{virtual} in any of its jargon senses.

	2. <mathematics> {real number}.

	[{Jargon File}]

	(1997-03-12)

<tool, cryptography> (PGP) A high security {RSA} {public-key
	encryption} application for {MS-DOS}, {Unix}, {VAX/VMS}, and
	other computers.  It was written by {Philip R. Zimmermann}
	<pkz@acm.org> of Phil's Pretty Good(tm) Software and later
	augmented by a cast of thousands, especially including Hal
	Finney, Branko Lankester, and Peter Gutmann.

	PGP was distributed as "{guerrilla freeware}".  The authors
	don't mind if it is distributed widely, just don't ask Philip
	Zimmermann to send you a copy.  PGP uses a {public-key
	encryption} {algorithm} claimed by US patent #4,405,829.  The
	exclusive rights to this patent are held by a California
	company called {Public Key Partners}, and you may be
	infringing this patent if you use PGP in the USA.  This is
	explained in the PGP User's Guide, Volume II.

	PGP allows people to exchange files or messages with {privacy}
	and {authentication}.  Privacy and authentication are provided
	without managing the keys associated with conventional
	cryptographic software.  No secure channels are needed to
	exchange keys between users, which makes PGP much easier to
	use.  This is because PGP is based on {public-key
	cryptography}.

	PGP encrypts data using the {International Data Encryption
	Algorithm} with a random {session key}, and uses the {RSA}
	algorithm to encrypt the session key.

	In December 1994 Philip Zimmermann faced prosecution for
	"exporting" PGP out of the United States but in January 1996
	the US Goverment dropped the case.  A US law prohibits the
	export of {encryption} software out of the country.
	Zimmermann did not do this, but the US government hoped to
	establish the proposition that posting an encryption program
	on a {BBS} or on the {Internet} constitutes exporting it - in
	effect, stretching export control into domestic censorship.
	If the government had won it would have had a chilling effect
	on the free flow of information on the global network, as well
	as on everyone's privacy from government snooping.

	{FAQ (ftp://ftp.netcom.com/pub/mp/mpj/getpgp.asc)}.  {UK FTP
	(ftp://src.doc.ic.ac.uk/packages/pgp/)}.  {USA FTP
	(http://web.mit.edu/network/pgp-form.html)}.
	{(http://www.pegasus.esprit.ec.org/people/arne/pgp.html)}.

	{Justice Dept. announcement
	(http://www.eff.org/pub/Alerts/usatty_pgp_011196.announce)}.

	["Protect Your Privacy: A Guide for PGP Users", William
	Stallings, Prentice-Hall, ISBN 0-13-185596-4].

	(1996-04-07)

<World-Wide Web> The {World-Wide Web} {search engine} that
	indexes the greatest number of web pages - over two billion by
	December 2001 and provides a free service that searches this
	index in less than a second.

	The site's name is apparently derived from "{googol}", but
	note the difference in spelling.

	The "Google" spelling is also used in "The Hitchhikers Guide
	to the Galaxy" by Douglas Adams, in which one of Deep
	Thought's designers asks, "And are you not," said Fook,
	leaning anxiously foward, "a greater analyst than the
	Googleplex Star Thinker in the Seventh Galaxy of Light and
	Ingenuity which can calculate the trajectory of every single
	dust particle throughout a five-week Dangrabad Beta sand
	blizzard?"

	{Home (http://www.google.com/)}.

	(2001-12-28)

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)

1. <programming> The prototype for an {object} in an
	{object-oriented language}; analogous to a {derived type} in a
	{procedural language}.  A class may also be considered to be a
	set of objects which share a common structure and behaviour.
	The structure of a class is determined by the {class
	variables} which represent the {state} of an object of that
	class and the behaviour is given by a set of {methods}
	associated with the class.

	Classes are related in a {class hierarchy}.  One class may be
	a specialisation (a "{subclass}") of another (one of its
	"{superclasses}") or it may be composed of other classes or it
	may use other classes in a {client-server} relationship.  A
	class may be an {abstract class} or a {concrete class}.

	See also {signature}.

	2. <programming> See {type class}.

	3. <networking> One of three types of {Internet addresses}
	distinguished by their most significant bits.

	3. <language> A language developed by the {Andrew Project}.
	It was one of the first attempts to add {object-oriented}
	features to {C}.

	(1995-05-01)

Said of a program or feature that is considered obsolescent
	and in the process of being phased out, usually in favour of a
	specified replacement.  Deprecated features can,
	unfortunately, linger on for many years.  This term appears
	with distressing frequency in standards documents when the
	committees writing the documents realise that large amounts of
	extant (and presumably happily working) code depend on the
	feature(s) that have passed out of favour.

	See also {dusty deck}.

	[{Jargon File}]

	(1995-04-19)

<jargon> A {marketroid} term for something he wants to sell
	you without bothering you with the often dizzying distinctions
	between {hardware}, {software}, {services}, {applications},
	{file formats}, companies, brand names and {operating
	systems}.

	"{Flash} is a perfect image-streaming solution."  "What is
	it?"  "Um...  about a thousand dollars."

	See also: {technology}.

	(1998-07-07)