<operating system, programming> The process of carrying out
	the {instructions} in a computer program by a computer.

	See also {dry run}.

	(1996-05-13)

<programming> (Or "arg") A value or reference passed to a
	{function}, {procedure}, {subroutine}, command or program, by
	the caller.  For example, in the function definition

		square(x) = x * x

	x is the {formal argument} or "parameter", and in the call

		y = square(3+4)

	3+4 is the {actual argument}.  This will execute the function
	square with x having the value 7 and return the result 49.

	There are many different conventions for passing arguments to
	functions and procedures including {call-by-value},
	{call-by-name}, {call-by-reference}, {call-by-need}.  These
	affect whether the value of the argument is computed by the
	caller or the callee (the function) and whether the callee can
	modify the value of the argument as seen by the caller (if it
	is a variable).

	Arguments to functions are usually, following mathematical
	notation, written in parentheses after the function name,
	separated by commas (but see {curried function}).  Arguments
	to a program are usually given after the command name,
	separated by spaces, e.g.:

		cat myfile yourfile hisfile

	Here "cat" is the command and "myfile", "yourfile", and
	"hisfile" are the arguments.

	(2006-05-27)

<programming> (Or "parameter") A name in a {function} or
	{subroutine} definition that is replaced by, or bound to, the
	corresponding {actual argument} when the function or
	subroutine is called.  In many languages formal arguments
	behave like {local variables} which get initialised on entry.

	See: {argument}.

	(2002-07-02)

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)

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)

<programming> (Sometimes "var" /veir/ or /var/) A named memory
	location in which a program can store intermediate results and
	from which it can read it them.  Each {programming language}
	has different rules about how variables can be named, typed,
	and used.  Typically, a value is "assigned" to a variable in
	an {assignment} statement.  The value is obtained by
	evaluating an expression and then stored in the variable.  For
	example, the assignment

		x = y + 1

	means "add one to y and store the result in x".  This may look
	like a mathematical equation but the mathematical equality is
	only true in the program until the value of x or y changes.
	Furthermore, statements like

		x = x + 1

	are common.  This means "add one to x", which only makes sense
	as a state changing operation, not as a mathematical equality.

	The simplest form of variable corresponds to a single-{word}
	of {memory} or a {CPU} {register} and an assignment to a
	{load} or {store} {machine code} operation.

	A variable is usually defined to have a {type}, which never
	changes, and which defines the set of values the variable can
	hold.  A type may specify a single ("atomic") value or a
	collection ("aggregate") of values of the same or different
	types.  A common aggregate type is the {array} - a set of
	values, one of which can be selected by supplying a numerical
	{index}.

	Languages may be {untyped}, {weakly typed}, {strongly typed},
	or some combination.  {Object-oriented programming} languages
	extend this to {object} types or {classes}.

	A variable's {scope} is the region of the program source
	within which it represents a certain thing.  Scoping rules are
	also highly language dependent but most serious languages
	support both {local variables} and {global variables}.
	{Subroutine} and {function} {formal arguments} are special
	variables which are set automatically by the language runtime
	on entry to the subroutine.

	In a {functional programming} language, a variable's value
	never changes and change of state is handled as recursion over
	lists of values.

	(2004-11-16)

1. <language> A simple, high-level interpreted language by
	Guido van Rossum <guido@cwi.nl>, 1991.  Python combines ideas
	from {ABC}, {C}, {Modula-3} and {Icon}.  It bridges the gap
	between {C} and {shell} programming, making it suitable for
	rapid prototyping or as an extension language for C
	applications.  It is {object-oriented} and supports packages,
	{modules}, {classes}, user-defined exceptions, a good C
	interface, dynamic loading of C modules and has no arbitrary
	restrictions.

	Python is available, among others, for {Unix}, {Windows},
	{DOS}, {OS/2}, {Macintosh}, and {Amoeba}.

	Current version: 1.4, includes {interpreter}, libraries, and
	documentation.

	{Home (http://www.python.org/)}.

	{Usenet} newsgroup: {news:comp.lang.python}.

	2. <compiler> A {compiler} for {CMU Common LISP}.  Python is
	more sophisticated than other {Common Lisp} compilers.  It
	produces better code and is easier to use.  The programming
	environment based on the {Hemlock} editor is better integrated
	than {GNU} {Emacs} based environments.

	(1997-02-27)

1. <hardware> An electrical conductor.  For distances larger
	than a breadbox, a single line may consist of two electrical
	conductors in twisted, parallel, or concentric arrangement
	used to transport one logical signal.

	By extension, a (usually physical) medium such as an {optical
	fibre} which carries a signal.

	(1995-09-29)

The stage in the {software life-cycle} at the end of the
	development process where software is evaluated to ensure that
	it complies with the requirements.

	(1995-02-14)

A group G is a non-empty {set} upon which a {binary} operator
	* is defined with the following properties for all a,b,c in G:

	  Closure:     G is closed under *,  a*b in G
	  Associative: * is associative on G, (a*b)*c = a*(b*c)
	  Identity:    There is an identity element  e  such that
		       a*e = e*a = a.
	  Inverse:     Every element has a unique inverse a' such that
		       a * a' = a' * a = e.  The inverse is usually
		       written with a superscript -1.

	(1998-10-03)

<artificial intelligence, information science> The objects,
	concepts and relationships that are assumed to exist in some
	area of interest.  A collection of {knowledge}, represented
	using some {knowledge representation} language is known as a
	{knowledge base} and a program for extending and/or querying a
	knowledge base is a {knowledge-based system}.

	Knowledge differs from {data} or {information} in that new
	knowledge may be created from existing knowledge using logical
	{inference}.  If information is data plus meaning then
	knowledge is information plus processing.

	A common form of knowledge, e.g. in a {Prolog} program, is a
	collection of {facts} and {rules} about some subject.

	For example, a {knowledge base} about a family might contain
	the facts that John is David's son and Tom is John's son and
	the rule that the son of someone's son is their grandson.
	From this knowledge it could infer the new fact that Tom is
	David's grandson.

	See also {Knowledge Level}.

	(1994-10-19)

1. (Obsolete) The source code for a program, which may be in
	any language, as opposed to the linkable or executable binary
	produced from it by a compiler.  The idea behind the term is
	that to a real hacker, a program written in his favourite
	programming language is at least as readable as English.
	Usage: mostly by old-time hackers, though recognisable in
	context.

	2. The official name of the {database} language used by the
	{Pick} {operating system}, actually a sort of {crufty},
	brain-damaged {SQL} with delusions of grandeur.  The name
	permits {marketroids} to say "Yes, and you can program our
	computers in English!" to ignorant {suits} without quite
	running afoul of the truth-in-advertising laws.

	["Exploring the Pick Operating System", J.E. Sisk et al,
	Hayden 1986].

	[{Jargon File}]

A distinctive style of shared intellectual humour found among
	hackers, having the following marked characteristics:

	1. Fascination with form-vs.-content jokes, paradoxes, and
	humour having to do with confusion of metalevels (see {meta}).
	One way to make a hacker laugh: hold a red index card in front
	of him/her with "GREEN" written on it, or vice-versa (note,
	however, that this is funny only the first time).

	2. Elaborate deadpan parodies of large intellectual
	constructs, such as specifications (see {write-only memory}),
	standards documents, language descriptions (see {INTERCAL}),
	and even entire scientific theories (see {quantum
	bogodynamics}, {computron}).

	3. Jokes that involve screwily precise reasoning from bizarre,
	ludicrous, or just grossly counter-intuitive premises.

	4. Fascination with puns and wordplay.

	5. A fondness for apparently mindless humour with subversive
	currents of intelligence in it - for example, old Warner
	Brothers and Rocky & Bullwinkle cartoons, the Marx brothers,
	the early B-52s, and Monty Python's Flying Circus.  Humour
	that combines this trait with elements of high camp and
	slapstick is especially favoured.

	6. References to the symbol-object antinomies and associated
	ideas in Zen Buddhism and (less often) Taoism.  See {has the X
	nature}, {Discordianism}, {zen}, {ha ha only serious}, {AI
	koan}.

	See also {filk} and {retrocomputing}.  If you have an itchy
	feeling that all 6 of these traits are really aspects of one
	thing that is incredibly difficult to talk about exactly, you
	are (a) correct and (b) responding like a hacker.  These
	traits are also recognizable (though in a less marked form)
	throughout {science-fiction fandom}.

	(1995-12-18)

<language, World-Wide Web> (DHTML) The addition of
	{JavaScript} to {HTML} to allow web pages to change and
	interact with the user without having to communicate with the
	server.  JavaScript allows the behaviour of the page to be
	controlled by code that is downloaded with the HTML.  It does
	this by manipulating the {Document Object Model} (DOM).

	The term DHTML is often also taken to include the use of
	"style" information to give finer control of HTML layout.  The
	style information can be supplied as {Cascading Style Sheets}
	(CSS) or as "style" attributes (which can be manipulated by
	JavaScript).  Layers are often also used with DHTML.

	Both the JavaScript and style data can be included in the HTML
	file or in a separate file referred to from the HTML.  Some
	web browsers allow other languages (e.g. {VBScript} or {Perl})
	to be used instead of JavaScript but this is less common.

	DHTML can be viewed in {Internet Explorer} 4+, {Firefox} and
	{Netscape} Communicator 4+ but, as usual, Microsoft disagree
	on how DHTML should be implemented.  The {Document Object
	Model} Group of the {World Wide Web Consortium} is developing
	standards for DHTML.

	{(http://www.w3c.org/DOM/)}.

	(2005-10-17)

1. As yet unexplained, or too complicated to explain; compare
	{automagically} and (Arthur C.) Clarke's Third Law:

		Any sufficiently advanced technology is
		indistinguishable from magic.

	"TTY echoing is controlled by a large number of magic bits."
	"This routine magically computes the parity of an 8-bit byte
	in three instructions."

	2. Characteristic of something that works although no one
	really understands why (this is especially called {black
	magic}).

	3. (Stanford) A feature not generally publicised that allows
	something otherwise impossible or a feature formerly in that
	category but now unveiled.

	Compare {wizardly}, {deep magic}, {heavy wizardry}.

	For more about hackish "magic" see {Magic Switch Story}.

	4. {magic number}.

	[{Jargon File}]

	(2001-03-19)

<convention, data> A string unique to a time duration of 24
	hours between 2 successive midnights defined by the local time
	zone.  The specific representation of a date will depend on
	which calendar convention is in force; e.g., Gregorian,
	Islamic, Japanese, Chinese, Hebrew etc. as well as local
	ordering conventions such as UK: day/month/year, US:
	month/day/year.

	Inputting and outputting dates on computers is greatly
	complicated by these {localisation} issues which is why they
	tend to operate on dates internally in some unified form such
	as seconds past midnight at the start of the first of January
	1970.

	Many software and hardware representations of dates allow only
	two digits for the year, leading to the {year 2000} problem.

	{Unix manual page}: date(1), ctime(3).

	(1997-07-11)

(MIT) An independent, coeducational university located in
	Cambridge, MA, USA.  Its best-known computer-related labs are
	the {Artificial Intelligence Lab}, the {Lab for Computer
	Science} and the Media Lab.  It is also known for its {hacks}
	or practical jokes, such as {The Great Dome Police Car Hack
	(http://the-tech.mit.edu/Bulletins/hack.html)}.  Resident
	computer {hackers} include {Richard Stallman}, {Gerald
	Sussman} and {Tom Knight}.

	See also {6.001}.

	{(http://web.mit.edu/)}.

<character> {hash}.

1. Non-functional; {down}; {crash}ed.  Especially used of
	{hardware}.

	2. At {XEROX PARC}, software that is working but not
	undergoing continued development and support.

	[{Jargon File}]

<mathematics> A function f : A -> B is surjective or onto or a
	surjection if f A = B.  I.e. f can return any value in B.
	This means that its {image} is its {codomain}.

	Only surjections have {right inverses}, f' : B -> A where
	f (f' x) = x since if f were not a surjection there would be
	elements of B for which f' was not defined.

	See also {bijection}, {injection}.

	(1995-05-27)

<storage, spelling> British spelling of "{disk}", normally
	only used for "{compact disc}".

	(1995-07-30)

<company> (BBC) The non-commercial UK organisation that
	commissions, produces and broadcasts television and radio
	programmes.

	The BBC commissioned the "{BBC Micro}" from {Acorn Computers}
	for use in a television series about using computers.  They
	also have one of the world's most respected news websites (on
	which I work!).

	{BBC Home (http://www.bbc.co.uk/)}.

	{BBC News (http://news.bbc.co.uk/)}.

	(2003-07-02)

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)

<computer, parallel> A {parallel processor} where tasks are
	distributed, or "farmed out", by one "farmer" processor to
	several "worker" processors, and results are sent back to the
	farmer.  This arrangement is suitable for {applications} which
	can be partitioned into many separate, independent tasks, the
	canonical examples being {ray tracing} and the {Mandelbrot
	set}.  In order to be efficient, the extra time spent on
	communications must be small compared to the time spent
	processing each task.

	(2001-05-28)

<language> An extensible language in the vein of {EL/1} and
	{RCC}.

	["Introduction to the Galaxy Language", Anne F. Beetem et al,
	IEEE Software 6(3):55-62].

	(1995-12-09)

<networking> Name Daemon.

	<networking> A {Unix} {background} process that converts
	{hostnames} to {Internet addresses} for the {TCP/IP}
	{protocol}.

	{Unix manual page}: named(8).

	See also {DNS}.

	(1995-03-28)

Common term for "computer", usually when considered at the
	hardware level.  The {Turing Machine}, an early example of
	this usage, was however neither hardware nor software, but
	only an idea.

	[Earlier use?]

	(1995-02-15)

<programming> (Or "remark") Explanatory text embedded in
	program {source} (or less often data) intended to help human
	readers understand it.

	Code completely without comments is often hard to read, but
	too heavily commented code isn't much better, especially if
	the comments are not kept up-to-date with changes to the code.
	Too much commenting may mean that the code is
	over-complicated.  A good rule is to comment everything that
	needs it but write code that doesn't need much of it.

	A particularly irksome form of over-commenting explains
	exactly what each statement does, even when it is obvious to
	any reasonably competant programmer, e.g.

		/* Open the input file */
		infd = open(input_file, O_RDONLY);

	(1998-04-28)

See {tuple}.

(Adelaide University, Australia) 1. Another {metasyntactic
	variable}.  See {foo}.  Derived originally from the Monty
	Python skit in the middle of "The Meaning of Life" entitled
	"Find the Fish".

	2. <storage> microfiche.  A microfiche file cabinet may be
	referred to as a "fish tank".

	[{Jargon File}]

	(1994-12-01)