<programming> (Or "computer program", "program", "code") The
	instructions executed by a computer, as opposed to the
	physical device on which they run (the "{hardware}").

	The term was coined by the eminent statistician, {John Tukey}.

	Programs stored on {non-volatile storage} built from
	{integrated circuits} (e.g. {ROM} or {PROM}) are usually
	called {firmware}.

	Software can be split into two main types - {system software}
	and application software or {application programs}.  System
	software is any software required to support the production or
	execution of application programs but which is not specific to
	any particular application.  Examples of system software would
	include the {operating system}, {compilers}, editors and
	sorting programs.

	Examples of application programs would include an accounts
	package or a {CAD} program.  Other broad classes of
	application software include {real-time} software, {business
	software}, scientific and engineering software, {embedded
	software}, personal computer software and {artificial
	intelligence} software.

	Software includes both {source code} written by humans and
	executable {machine code} produced by {assemblers} or
	{compilers}.  It does not usually include the data processed
	by programs unless this is in a format such as {multimedia}
	which depends on the use of computers for its presentation.
	This distinction becomes unclear in cases such as {spread
	sheets} which can contain both instructions (formulae and
	{macros}) and data.  There are also various intermediate
	compiled or {semi-compiled}, forms of software such as
	{library} files and {byte-code}.

	Some claim that {documentation} (both paper and electronic) is
	also software.  Others go further and define software to be
	programs plus documentation though this does not correspond
	with common usage.

	The noun "program" describes a single, complete and
	more-or-less self-contained list of instructions, often stored
	in a single {file}, whereas "code" and "software" are
	uncountable nouns describing some number of instructions which
	may constitute one or more programs or part thereof.  Most
	programs, however, rely heavily on various kinds of {operating
	system} software for their execution.  The nounds "code" and
	"software" both refer to the same thing but "code" tends to
	suggest an interest in the implementation details whereas
	"software" is more of a user's term.

	(2002-07-21)

1. <mathematics> (Or "map", "mapping") If D and C are sets
	(the domain and codomain) then a function f from D to C,
	normally written "f : D -> C" is a subset of D x C such that:

	1. For each d in D there exists some c in C such that (d,c) is
	an element of f.  I.e. the function is defined for every
	element of D.

	2. For each d in D, c1 and c2 in C, if both (d,c1) and (d,c2)
	are elements of f then c1 = c2.  I.e. the function is uniquely
	defined for every element of D.

	See also {image}, {inverse}, {partial function}.

	2. <programming> Computing usage derives from the mathematical
	term but is much less strict.  In programming (except in
	{functional programming}), a function may return different
	values each time it is called with the same argument values
	and may have {side effects}.

	A {procedure} is a function which returns no value but has
	only {side-effects}.  The {C} language, for example, has no
	procedures, only functions.  {ANSI C} even defines a {type},
	{void}, for the result of a function that has no result.

	(1996-09-01)

<programming> A {function}, {operator}, or {type} which is
	built into a programming language (or {operating system}),
	either for speed of execution or because it would be
	impossible to write it in the language.  Primitives typically
	include the arithmetic and logical operations (plus, minus,
	and, or, etc.) and are implemented by a small number of
	{machine language} instructions.

	(1995-05-01)

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)

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)

<messaging> (e-mail) Messages automatically passed from one
	computer user to another, often through computer {networks}
	and/or via {modems} over telephone lines.

	A message, especially one following the common {RFC 822}
	{standard}, begins with several lines of {headers}, followed
	by a blank line, and the body of the message.  Most e-mail
	systems now support the {MIME} {standard} which allows the
	message body to contain "{attachments}" of different kinds
	rather than just one block of plain {ASCII} text.  It is
	conventional for the body to end with a {signature}.

	Headers give the name and {electronic mail address} of the
	sender and recipient(s), the time and date when it was sent
	and a subject.  There are many other headers which may get
	added by different {message handling systems} during delivery.

	The message is "composed" by the sender, usually using a
	special program - a "{Mail User Agent}" (MUA).  It is then
	passed to some kind of "{Message Transfer Agent}" (MTA) - a
	program which is responsible for either delivering the message
	locally or passing it to another MTA, often on another {host}.
	MTAs on different hosts on a network often communicate using
	{SMTP}.  The message is eventually delivered to the
	recipient's {mailbox} - normally a file on his computer - from
	where he can read it using a mail reading program (which may
	or may not be the same {MUA} as used by the sender).

	Contrast {snail-mail}, {paper-net}, {voice-net}.

	The form "email" is also common, but is less suggestive of the
	correct pronunciation and derivation than "e-mail".  The word
	is used as a noun for the concept ("Isn't e-mail great?", "Are
	you on e-mail?"), a collection of (unread) messages ("I spent
	all night reading my e-mail"), and as a verb meaning "to send
	(something in) an e-mail message" ("I'll e-mail you (my
	report)").  The use of "an e-mail" as a count noun for an
	e-mail message, and plural "e-mails", is now (2000) also well
	established despite the fact that "mail" is definitely a mass
	noun.

	Oddly enough, the word "emailed" is actually listed in the
	Oxford English Dictionary.  It means "embossed (with a raised
	pattern) or arranged in a net work".  A use from 1480 is
	given.  The word is derived from French "emmailleure",
	network.  Also, "email" is German for enamel.

	{The story of the first e-mail message
	(http://www.pretext.com/mar98/features/story2.htm)}.

	(2002-07-14)

<tool> A program to allow a file to be read (or played) but
	not changed.  Viewers are often freely distributable, even
	when the editor application is not.  This allows you to create
	files with the editor and make the viewer available to other
	users to view your files, e.g. on a {website}.  Examples
	include the Word and Adobe Acrobat viewers.

	(1997-08-29)

1. <unit, text> (Sometimes abbreviated "pt") The unit of
	length used in {typography} to specify text character height,
	{rule} width, and other small measurements.

	There are six slightly different definitions: {Truchet point},
	{Didot point}, {ATA point}, {TeX point}, {Postscript point},
	and {IN point}.

	In Europe, the most commonly used is Didot and in the US, the
	formerly standard ATA point has essentially been replaced by
	the PostScript point due to the demise of traditional
	typesetting systems and rise of desktop computer based systems
	running software such as {QuarkXPress}, {Adobe InDesign} and
	{Adobe Pagemaker}.

	There are 20 {twips} in a point and 12 points in a {pica}
	(known as a "Cicero" in the Didot system).

	{Different point systems
	(http://www.vakcer.com/oberon/dtp/fonts/point.htm)}.

	(2004-12-23)

	2. <hardware> To move a {pointing device} so that the
	on-screen pointer is positioned over a certain object on the
	screen such as a {button} in a {graphical user interface}.  In
	most {window systems} it is then necessary to {click} a
	(physical) button on the pointing device to activate or select
	the object.  In some systems, just pointing to an object is
	known as "mouse-over" {event} which may cause some help text
	(called a "tool tip" in {Windows}) to be displayed.

	(2001-05-21)

<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)

<storage, architecture, jargon, theory> How something is; its
	configuration, attributes, condition, or information content.
	The state of a system is usually temporary (i.e. it changes
	with time) and volatile (i.e. it will be lost or reset to some
	initial state if the system is switched off).

	A state may be considered to be a point in some {space} of all
	possible states.  A simple example is a light, which is either
	on or off.  A complex example is the electrical activation in
	a human brain while solving a problem.

	In computing and related fields, states, as in the light
	example, are often modelled as being {discrete} (rather than
	continuous) and the transition from one state to another is
	considered to be instantaneous.  Another (related) property of
	a system is the number of possible states it may exhibit.
	This may be finite or infinite.  A common model for a system
	with a finite number of discrete state is a {finite state
	machine}.

	[{Jargon File}]

	(1996-10-13)

[slang "big wheel" for a powerful person] A person who has an
	active {wheel bit}.  "We need to find a wheel to unwedge the
	hung tape drives."  (See {wedged}).

	[{Jargon File}]

1. <chat> {Unix}'s simple {talk} command and {protocol}.
	write has been largely superseded by {talk} and then {irc}.

	An enhancement, {RWP}, has been proposed.

	2. <tool> A simple {text editor} for {Windows}.

	(1998-04-28)

<programming> (Or "procedure") A sequence of {instructions}
	for performing a particular task.  Most programming languages,
	including most {machine languages}, allow the programmer to
	define subroutines.  This allows the subroutine code to be
	called from multiple places, even from within itself (in which
	case it is called {recursive}).  The programming language
	implementation takes care of returning control to (just after)
	the calling location, usually with the support of call and
	return instructions at {machine language} level.

	Most languages also allow {arguments} to be passed to the
	subroutine, and one, or occasionally more, {return values} to
	be passed back.

	A {function} is often very similar to a subroutine, the main
	difference being that it is called chiefly for its return
	value, rather than for any {side effects}.

	(1996-10-01)

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)

<character> (Or "ctrl", "^") One (or a pair) of {modifier
	keys} found on all modern {keyboards}.  If the control key is
	held down while pressing and releasing certain other keys then
	a "{control character}" is generated, e.g. holding control and
	hitting "A" generates control-A ({ASCII} code 1).  The ASCII
	code for the control character is generally 64 less than that
	for the unmodified character.

	The control key does not generate any character on its own but
	most modern keyboards and {operating systems} allow a program
	to tell whether each of the individual keys on the keyboard
	(including modifier keys) is pressed at any time.

	Control characters mostly have some kind of "non-printing"
	effect on the output such as ringing the bell (Control-G) or
	advancing to the next line (Control-J).  Most have alternative
	names suggesting these functions (Bell, Line Feed, etc.).

	See {ASCII character table}.

	(1997-07-10)

<digital signal processing> The result of measuring the
	amplitude of an analog signal at a specified time.  In
	{digital signal processing} a sample is a signed or unsigned
	number and the number of samples per second is called the
	{sample rate}.

	(2001-06-06)

1. To prepare to read or write a file.  This usually involves
	checking whether the file already exists and that the user has
	the necessary authorisation to read or write it.  The result
	of a successful open is usually some kind of {capability}
	(e.g. a {Unix} {file descriptor}) - a token that the user
	passes back to the system in order to access the file without
	further checks and finally to close the file.

	2. Abbreviation for "open (or left) parenthesis" - used when
	necessary to eliminate oral ambiguity.  To read aloud the LISP
	form (DEFUN FOO (X) (PLUS X 1)) one might say: "Open defun
	foo, open eks close, open, plus eks one, close close."

	3. Non-proprietary.  An open {standard} is one which can be
	used without payment.

	[{Jargon File}]

	(1995-01-31)

<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)

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)

<data processing, signal processing> Performing some
	predefined sequence of operations on an input to produce an
	output or change of internal state; activity specifically
	involving the computer's {CPU}.

	The term is often qualified: "{data processing}" treats
	{digital} data, "{signal processing}" treats {analog} data
	(possibly in digital form), "{word processing}" takes in typed
	human language input and produces digital documents, {image
	processing} transforms digital {images}.

	(2003-10-23)