1. <World-Wide Web> {HTTP cookie}.

	2. <protocol> A handle, transaction ID, or other token of
	agreement between cooperating programs.  "I give him a packet,
	he gives me back a cookie".

	The ticket you get from a dry-cleaning shop is a perfect
	mundane example of a cookie; the only thing it's useful for is
	to relate a later transaction to this one (so you get the same
	clothes back).

	Compare {magic cookie}; see also {fortune cookie}.

	3. <security, jargon> A {cracker} term for the {password} list
	on a {multi-user} computer.

	4. <jargon> An adjective describing a computer that just
	became {toast}.

	(1997-04-14)

<networking> 1. A lasting connection between a user (or user
	agent) and a {peer}, typically a {server}, usually involving
	the exchange of many packets between the user's computer and
	the server.  A session is typically implemented as a layer in
	a network {protocol} (e.g. {telnet}, {FTP}).

	In the case of protocols where there is no concept of a
	session layer (e.g. {UDP}) or where sessions at the {session
	layer} are generally very short-lived (e.g. {HTTP}), {virtual}
	sessions are implemented by having each exchange between the
	user and the remote host include some form of {cookie} which
	stores state (e.g. a unique session ID, information about the
	user's preferences or authorisation level, etc.).

	See also {login}.

	2. A lasting connection using the {session layer} of a
	networking protocol.

	(1997-08-03)

<text> The spacing between {characters} in a line of {text}.
	This is defined when a {font} is designed but can often be
	altered in order to change the appearance of the text or for
	special effects.

	Tracking should not be confused with {kerning} which deals
	with the spacing between certain pairs of characters.

	See also {leading}.

	(1996-06-07)

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. 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)

1. <jargon> {login}.

	2. <networking> In {ACF}/{VTAM}, an unformatted
	session-initiation request for a session between two {logical
	units}.

	(1996-03-07)

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)

1. <networking> {e-mail address}.

	2. <networking> {Internet address}.

	3. <networking> {MAC address}.

	4. <storage, programming> An unsigned integer used to select
	one fundamental element of storage, usually known as a {word}
	from a computer's {main memory} or other storage device.  The
	{CPU} outputs addresses on its {address bus} which may be
	connected to an {address decoder}, {cache controller}, {memory
	management unit}, and other devices.

	While from a hardware point of view an address is indeed an
	integer most {strongly typed} programming languages disallow
	mixing integers and addresses, and indeed addresses of
	different data types.  This is a fine example for {syntactic
	salt}: the compiler could work without it but makes writing
	bad programs more difficult.

	(1997-07-01)

1. <programming> A property of a programming language where
	created objects and variables continue to exist and retain
	their values between runs of the program.

	2. <hardware> The length of time a phosphor dot on the screen
	of a {cathode ray tube} will remain illuminated after it has
	been energised by the electron beam.  Long-persistence
	phosphors reduce flicker, but generate ghost-like images that
	linger on screen for a fraction of a second.

	(1994-11-09)

<company> (IBM) The best known American computer manufacturer,
	founded by Thomas J. Watson (born 1874-02-17), known as "Big
	Blue" after the colour of its logo.  IBM makes everything from
	{mainframes} to {personal computers} (PCs) and has been
	immensely successful in selling them, chiefly to business.  It
	has often been said that "Nobody has ever been sacked for
	buying IBM".

	The {IBM PC} in its various versions has been so successful
	that unqualified reference to a "PC" almost certainly means a
	PC from IBM, or one of the many brands of {clone} produced by
	other manufacturers to cash in on IBM's original success.

	Alternative expansions of "IBM" such as Inferior But
	Marketable; It's Better Manually; Insidious Black Magic; It's
	Been Malfunctioning; Incontinent Bowel Movement, illustrate
	the considerable antipathy most hackers have long felt toward
	the "industry leader" (see {fear and loathing}).

	Quarterly sales $15351M, profits $689M (Aug 1994).

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

	(1999-04-07)

<language, tool> A {Unix} tool written in {Tcl} and a {script
	language} for automating the operation of {interactive}
	applications such as {telnet}, {FTP}, {passwd}, {fsck},
	{rlogin}, {tip}, etc..  Expect can feed input to other
	programs and perform {pattern matching} on their output.  It
	is also useful for testing these applications.  By adding
	{Tk}, you can also wrap interactive applications in {X11}
	{GUIs}.

	{Home (http://expect.nist.gov/)}.

	["expect: Scripts for Controlling Interactive Tasks", Don
	Libes, Comp Sys 4(2), U Cal Press Journals, Nov 1991].

	(1997-06-09)

<mathematics> A real-valued {function} modelling the length of
	a {vector}.  The norm must be {homogeneous} and {symmetric}
	and fulfil the following condition: the shortest way to reach
	a point is to go straight toward it.  Every {convex} symmetric
	{closed} surface surrounding point 0 introduces a norm by
	means of {Minkowski functional}; all vectors that end on the
	surface have the same norm then.

	The most popular norm is the {Euclidean norm}.

	(2004-02-15)

1. <file system> {hard link} or {symbolic link}.

	2. <hypertext> {hyperlink}.

	(1997-10-22)

<World-Wide Web> (URL, previously "Universal") A {standard}
	way of specifying the location of an object, typically a {web
	page}, on the {Internet}.  Other types of object are described
	below.  URLs are the form of address used on the {World-Wide
	Web}.  They are used in {HTML} documents to specify the target
	of a {hyperlink} which is often another HTML document
	(possibly stored on another computer).

	Here are some example URLs:

	 http://www.w3.org/default.html
	 http://www.acme.co.uk:8080/images/map.gif
	 http://www.foldoc.org/?Uniform+Resource+Locator
	 http://www.w3.org/default.html#Introduction
	 ftp://wuarchive.wustl.edu/mirrors/msdos/graphics/gifkit.zip
	 ftp://spy:secret@ftp.acme.com/pub/topsecret/weapon.tgz
	 mailto:fred@doc.ic.ac.uk
	 news:alt.hypertext
	 telnet://dra.com

	The part before the first colon specifies the access scheme or
	{protocol}.  Commonly implemented schemes include: {ftp},
	{http} (World-Wide Web), {gopher} or {WAIS}.  The "file"
	scheme should only be used to refer to a file on the same
	host.  Other less commonly used schemes include {news},
	{telnet} or mailto ({e-mail}).

	The part after the colon is interpreted according to the
	access scheme.  In general, two slashes after the colon
	introduce a {hostname} (host:port is also valid, or for {FTP}
	user:passwd@host or user@host).  The {port} number is usually
	omitted and defaults to the standard port for the scheme,
	e.g. port 80 for HTTP.

	For an HTTP or FTP URL the next part is a {pathname} which is
	usually related to the pathname of a file on the server.  The
	file can contain any type of data but only certain types are
	interpreted directly by most {browsers}.  These include {HTML}
	and images in {gif} or {jpeg} format.  The file's type is
	given by a {MIME} type in the HTTP headers returned by the
	server, e.g. "text/html", "image/gif", and is usually also
	indicated by its {filename extension}.  A file whose type is
	not recognised directly by the browser may be passed to an
	external "viewer" {application}, e.g. a sound player.

	The last (optional) part of the URL may be a query string
	preceded by "?" or a "fragment identifier" preceded by "#".
	The later indicates a particular position within the specified
	document.

	Only alphanumerics, reserved characters (:/?#"<>%+) used for
	their reserved purposes and "$", "-", "_", ".", "&", "+" are
	safe and may be transmitted unencoded.  Other characters are
	encoded as a "%" followed by two {hexadecimal} digits.  Space
	may also be encoded as "+".  Standard {SGML} "&<name>;"
	character entity encodings (e.g. "&eacute;") are also accepted
	when URLs are embedded in HTML.  The terminating semicolon may
	be omitted if &<name> is followed by a non-letter character.

	{The authoritative W3C URL specification
	(http://www.w3.org/hypertext/WWW/Addressing/Addressing.html)}.

	(2000-02-17)

1. Corporate power elites distinguished primarily by their
	distance from actual productive work and their chronic failure
	to manage (see also {suit}).  Spoken derisively, as in
	"*Management* decided that ...".

	2. Mythically, a vast bureaucracy responsible for all the
	world's minor irritations.  Hackers' satirical public notices
	are often signed "The Mgt"; this derives from the
	"Illuminatus!" novels.

	[{Jargon File}]

	(1995-02-28)

1. <grammar> A basic, grammatically indivisible unit of a
	language such as a {keyword}, operator or identifier.
	Compare: {lexeme}.

	2. <convention> (Or "{pumpkin}") An abstact concept passed
	between cooperating agents to ensure synchronised access to a
	shared resource.  Such a token is never duplicated or
	destroyed (unless the resource is) and whoever has the token
	has exclusive access to the resource it controls.  See for
	example {token ring}.

	If several programmers are working on a program, one
	programmer will "have the token" at any time, meaning that
	only he can change the program whereas others can only read
	it.  If someone else wants to modify it he must first obtain
	the token.

	(1999-02-23)

<hypertext> A program which allows a person to read
	{hypertext}.  The browser gives some means of viewing the
	contents of {nodes} (or "pages") and of {navigating} from one
	node to another.

	{Netscape Navigator}, {NCSA} {Mosaic}, {Lynx}, and {W3} are
	examples for browsers for the {World-Wide Web}.  They act as
	{clients} to remote {web servers}.

	(1996-05-31)

To produce something according to an {algorithm} or program or
	set of rules, or as a (possibly unintended) {side effect} of
	the execution of an algorithm or program.

	The opposite of {parse}.

	[{Jargon File}]

	(1995-06-15)

<communications> Playing {sound} or {video} in {real time} as
	it is downloaded over the {Internet} as opposed to storing it
	in a local file first.  A {plug-in} to a {web browser} such as
	{Netscape Navigator} decompresses and plays the data as it is
	transferred to your computer over the {World-Wide Web}.
	Streaming audio or video avoids the delay entailed in
	downloading an entire file and then playing it with a {helper
	application}.  Streaming requires a fast connection and a
	computer powerful enough to execute the decompression
	{algorithm} in {real time}.

	(1996-11-06)

1. <networking> {network}.

	2. <networking> {network, the}.

	3. <architecture> {neural network}.

	4. <networking> The {top-level domain} originally for
	networks, although it sees heavy use for {vanity domains} of
	all types.

	[{Jargon File}]

	(1999-01-26)

1. The {supervisor} program or {operating system} on a
	computer.

	2. The entire computer system, including input/output devices,
	the {supervisor} program or {operating system} and possibly
	other {software}.

	3. Any large program.

	4. Any method or {algorithm}.

	[{Jargon File}]

<storage> These days, usually used synonymously with {Random
	Access Memory} or {Read-Only Memory}, but in the general sense
	it can be any device that can hold {data} in
	{machine-readable} format.

	(1996-05-25)

1. A circuit board.

	2. A {punched card}.

	3. <hypertext> An alternative term for a {node} in a system
	(e.g. {HyperCard}, {Notecards}) in which the node size is
	limited.

On {Usenet}, a {posting} generated in response to another
	posting (as opposed to a {reply}, which goes by e-mail rather
	than being broadcast).  Followups include the ID of the
	{parent message} in their headers; smart news-readers can use
	this information to present {Usenet} news in "conversation"
	sequence rather than order-of-arrival.  See {thread}.

	[{Jargon File}]

<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)

1. The art of debugging a blank sheet of paper (or, in these
	days of on-line editing, the art of debugging an empty file).

	2. A pastime similar to banging one's head against a wall, but
	with fewer opportunities for reward.

	3. The most fun you can have with your clothes on (although
	clothes are not mandatory).

	[{Jargon File}]

	(2003-02-12)

<World-Wide Web> (By analogy with "{applet}") A {Java} program
	that runs as part of a {network} service, typically an {HTTP
	server} and responds to requests from {clients}.

	The most common use for a servlet is to extend a {web server}
	by generating {web content} dynamically.  For example, a
	{client} may need {information} from a {database}; a servlet
	can be written that receives the request, gets and processes
	the data as needed by the {client} and then returns the result
	to the {client}.

	{Applets} are also written in {Java} but run inside the {JVM}
	of a {HTML} {browser} on the {client}.  Servlets and applets
	allow the server and client to be extended in a modular way by
	dynamically loading code which communicates with the main
	program via a standard programming interface.

	Servlets are more flexible than {CGI scripts} and, being
	written in {Java}, more portable.

	The spelling "servelet" is occasionally seen but {JavaSoft}
	spell it "servlet".  There is no such thing as a "serverlet".

	{(http://java.sun.com/products/servlet/)}.

	(2002-10-06)

The process of analysis, design, coding and testing software.

1. <software> An occurrence or happening of significance to a
	task or program, such as the completion of an asynchronous
	input/output operation.  A task may wait for an event or any
	of a set of events or it may (request to) receive asynchronous
	notification (a {signal} or {interrupt}) that the event has
	occurred.

	See also {event-driven}.

	2. <data> A transaction or other activity that affects the
	records in a file.

	(2000-02-09)

<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> (Or "branch") The term for a {goto} instruction,
	usually in a context of {machine languages}.  "Branch" may be
	synonymous with "jump", or may refer to jumps that depend on a
	condition.

	(1998-11-14)