<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)

<language>

	1. A {relational language} designed by Jones and M. Sheeran in
	1986 for describing and designing circuits (a {hardware
	description language}).  Ruby programs denote {binary
	relations} and programs are built-up inductively from
	primitive relations using a pre-defined set of {relational
	operators}.  Ruby programs also have a geometric
	interpretation as networks of primitive relations connected by
	wires, which is important when layout is considered in circuit
	design.

	Ruby has been continually developed since 1986, and has been
	used to design many different kinds of circuits, including
	{systolic arrays}, {butterfly networks} and arithmetic
	circuits.

	{(ftp://ftp.cs.chalmers.se/pub/misc/ruby/)}.

	E-mail: <graham@cs.chalmers.se>.

	["Ruby - A Language of Relations and Higher-Order Functions",
	M. Sheeran, Proc 3rd Banff Workshop on Hardware Verification,
	Springer 1990].

	(1994-10-27)

	2. One of five pedagogical languages based on {Markov
	algorithms}, used in Higman's report (below).  The other
	languages are {Brilliant}, {Diamond}, {Nonpareil}, and
	{Pearl}.

	["Nonpareil, a Machine Level Machine Independent Language for
	the Study of Semantics", B. Higman, ULICS Intl Report No ICSI
	170, U London (1968)].

	(1994-10-27)

	3. A fully {object oriented} {interpreted} {scripting
	language} by Yukihiro Matsumoto <matz@netlab.co.jp>.

	Similar in scope to {Perl} and {Python}, Ruby has high-level
	{data types}, automatic {memory management}, {dynamic typing},
	a {module} system, {exceptions}, and a rich standard library.
	Other features are {CLU}-style {iterators} for {loop
	abstraction}, {singleton classes}/{methods} and {lexical
	closures}.

	In Ruby, everything is an {object}, including the basic data
	types.  For example, the number 1 is an instance of {class}
	Fixnum.

	Current version (stable): 1.6.7, as of 2002-03-01.

	{Ruby Home (http://www.ruby-lang.org/)}.

	{Ruby Central (http://www.rubycentral.com/)}.

	["Programming Ruby - The Pragmatic Programmer's Guide", David
	Thomas, Andrew Hunt, Yukihiro Matsumoto pub. Addison Wesley
	2000].

	(2002-06-19)

<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)

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)

<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 {cathode-ray tube} and associated electronics connected
	to a computer's video output.  A monitor may be either
	{monochrome} (black and white) or colour ({RGB}).  Colour
	monitors may show either digital colour (each of the red,
	green and blue signals may be either on or off, giving eight
	possible colours: black, white, red, green, blue, cyan,
	magenta and yellow) or analog colour (red, green and blue
	signals are continuously variable allowing any combination to
	be displayed).  Digital monitors are sometimes known as {TTL}
	because the voltages on the red, green and blue inputs are
	compatible with TTL logic chips.

	See also {gamut}, {multisync}, {visual display unit}.

	2. A programming language construct which encapsulates
	variables, access procedures and initialisation code within an
	abstract data type.  The monitor's variable may only be
	accessed via its access procedures and only one process may be
	actively accessing the monitor at any one time.  The access
	procedures are {critical sections}.  A monitor may have a
	queue of processes which are waiting to access it.

	3. A hardware device that measures electrical events such as
	pulses or voltage levels in a digital computer.

	4. To oversee a program during execution.  For example, the
	monitor function in the {Unix} {C} library enables profiling
	of a certain range of code addresses.  A histogram is produced
	showing how often the {program counter} was found to be at
	each position and how often each profiled function was called.

	{Unix} {man} page: monitor(3).

	5. A control program within the {operating system} that
	manages the allocation of system resources to active
	programs.

	6. A program that measures software performance.

<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)

A group of {application programs} from {Lotus Development
	Corporation} which allows organisations to share documents and
	exchange {electronic mail} messages.  Notes supports
	{replication}.

	(1994-10-27)

<messaging> (Plural "fora" or "forums") Any discussion group
	accessible through a dial-in {BBS} (e.g. {GEnie}, {CI$}), a
	{mailing list}, or a {Usenet} {newsgroup} (see {network,
	the}).  A forum functions much like a {bulletin board}; users
	submit {postings} for all to read and discussion ensues.

	Contrast real-time {chat} or point-to-point personal {e-mail}.

	[{Jargon File}]

	(1998-01-18)

<jargon> A boundary across which two systems communicate.  An
	interface might be a hardware connector used to link to other
	devices, or it might be a convention used to allow
	communication between two software systems.  Often there is
	some intermediate component between the two systems which
	connects their interfaces together.  For example, two {EIA-232}
	interfaces connected via a serial cable.

	See also {graphical user interface}, {Application Program
	Interface}.

	(1996-05-22)

<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)

<hypertext, World-Wide Web, standard> (HTML) A {hypertext}
	document format used on the {World-Wide Web}.  HTML is built
	on top of {SGML}.  "Tags" are embedded in the text.  A tag
	consists of a "<", a "directive" (in lower case), zero or
	more parameters and a ">".  Matched pairs of directives, like
	"<title>" and "</title>" are used to delimit text which is to
	appear in a special place or style.

	Links to other documents are in the form

	 <a href="http://machine.edu/subdir/file.html">foo</a>

	where "<a>" and "</a>" delimit an "anchor", "href" introduces
	a hypertext reference, which is most often a {Uniform Resource
	Locator} (URL) (the string in double quotes in the example
	above).  The link will be represented in the browser by the
	text "foo" (typically shown underlined and in a different
	colour).

	A certain place within an HTML document can be marked with a
	named anchor, e.g.:

	 <a name="baz">

	The "fragment identifier", "baz", can be used in an href by
	appending "#baz" to the document name.

	Other common tags include <p> for a new paragraph, <b>..</b>
	for bold text, <ul> for an unnumbered list, <pre> for
	preformated text, <h1>, <h2> .. <h6> for headings.

	{HTML} supports some standard {SGML} {national characters} and
	other non-{ASCII} characters through special {escape
	sequences}, e.g. "&eacute;" for a lower case 'e' with an acute
	accent.  You can sometimes get away without the terminating
	semicolon but it's bad style.

	Most systems will ignore the case of tags and attributes but
	lower case should be used for compatibility with {XHTML}.

	The {World-Wide Web Consortium} (W3C) is the international
	{standards} body for HTML.

	Latest version: {XHTML} 1.0, as of 2000-09-10.

	{Home (http://www.w3.org/MarkUp/)}.

	{Character escape sequences
	(http://www.w3.org/hypertext/WWW/MarkUp/ISOlat1.html)}.

	See also {weblint}.

	(2006-01-19)

<convention> (FAQ, or rarely FAQL, FAQ list) A document
	provided for many {Usenet} {newsgroups} (and, more recently,
	{World-Wide Web} services) which attempts to answer questions
	which new readers often ask.  These are maintained by
	volunteers and posted regularly to the newsgroup.  You should
	always consult the FAQ list for a group before posting to it
	in case your question or point is common knowledge.

	The collection of all FAQ lists is one of the most precious
	and remarkable resources on the {Internet}.  It contains a
	huge wealth of up-to-date expert knowledge on many subjects of
	common interest.  Accuracy of the information is greatly
	assisted by its frequent exposure to criticism by an
	interested, and occasionally well-informed, audience (the
	readers of the relevant newsgroup).

	The main {FTP archive} for FAQs is on a computer called {RTFM}
	at {MIT}, where they can be accessed either {by group
	(ftp://rtfm.mit.edu/pub/usenet-by-group/comp.answers/)} or {by
	hierarchy (ftp://rtfm.mit.edu/pub/usenet-by-hierarchy/)}.
	There is another archive at {Imperial College
	(ftp://src.doc.ic.ac.uk/usenet/news-info/)}, London, UK and a
	{World-Wide Web} archive in {Ohio
	(http://www.cis.ohio-state.edu/hypertext/faq/usenet/top.html)},
	USA.

	The FAQs are also posted to {Usenet} newsgroups:
	{news:comp.answers}, {news:news.answers} and
	{news:alt.answers}.

	(1997-12-08)

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)

1. Executable code, especially a "pure code" portion shared
	between multiple instances of a program running in a
	{multitasking} {operating system}.

	Compare {English}.

	2. Textual material in the mainstream sense; data in ordinary
	{ASCII} or {EBCDIC} representation (see {flat ASCII}).  "Those
	are text files; you can review them using the editor."

	These two contradictory senses confuse hackers too.

	[{Jargon File}]

	(1995-03-16)

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)

1. <programming> An independent piece of {software} which
	forms part of one or more larger {programs}.  Different
	languages have different concepts of a module but there are
	several common ideas.

	Modules are usually compiled seperately (in compiled
	languages) and provide an {abstraction} or information hiding
	mechanism so that a module's implementation can be changed
	without requiring any change to other modules.  In this
	respect they are similar to {objects} in an {object-oriented
	language}, though a module may contain many {procedures}
	and/or {functions} which would correspond to many objects.

	A module often has its own {name space} for {identifiers} so
	the same identifier may be used to mean different things in
	different modules.

	[Difference from {package}?].

	2. <hardware> An independent assembly of electronic components
	with some distinct function, e.g. a RAM module consisting of
	several RAM chips mounted on a small circuit board.

	(1997-10-27)

<programming> (API, or "application programming interface")
	The interface (calling conventions) by which an {application
	program} accesses {operating system} and other services.  An
	API is defined at {source code} level and provides a level of
	{abstraction} between the application and the {kernel} (or
	other privileged utilities) to ensure the {portability} of the
	code.

	An API can also provide an interface between a {high level
	language} and lower level utilities and services which were
	written without consideration for the {calling conventions}
	supported by compiled languages.  In this case, the API's main
	task may be the translation of parameter lists from one format
	to another and the interpretation of {call-by-value} and
	{call-by-reference} arguments in one or both directions.

	(1995-02-15)

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)

1. <unit> The standard metric prefixes used in the {Systme
	International d'Units} (SI) conventions for scientific
	measurement.

	Here are the SI magnifying prefixes, along with the
	corresponding binary interpretations in common use:

	 prefix abr decimal  binary

	 yocto-     1000^-8
	 zepto-     1000^-7
	 atto-      1000^-6
	 femto-  f  1000^-5
	 pico-   p  1000^-4
	 nano-   n  1000^-3
	 micro-  *  1000^-2          * Abbreviation: Greek mu
	 milli-  m  1000^-1

	 kilo- 	 k  1000^1  1024^1 = 2^10 = 1,024
	 mega- 	 M  1000^2  1024^2 = 2^20 = 1,048,576
	 giga- 	 G  1000^3  1024^3 = 2^30 = 1,073,741,824
	 tera- 	 T  1000^4  1024^4 = 2^40 = 1,099,511,627,776
	 peta- 	    1000^5  1024^5 = 2^50 = 1,125,899,906,842,624
	 exa-  	    1000^6  1024^6 = 2^60 = 1,152,921,504,606,846,976
	 zetta-     1000^7  1024^7 = 2^70 = 1,180,591,620,717,411,303,424
	 yotta-     1000^8  1024^8 = 2^80 = 1,208,925,819,614,629,174,706,176

	"Femto" and "atto" derive not from Greek but from Danish.

	The abbreviated forms of these prefixes are common in
	electronics and physics.

	When used with bytes of storage, these prefixes usually denote
	multiplication by powers of 1024 = 2^10 (K, M, and G are
	common in computing).  Thus "MB" stands for megabytes (2^20
	bytes).  This common practice goes against the edicts of the
	{BIPM} who deprecate the use of these prefixes for powers of
	two.  The formal SI prefix for 1000 is lower case "k"; some,
	including this dictionary, use this strictly, reserving upper
	case "K" for multiplication by 1024 (KB is thus "kilobytes").

	Also, in data transfer rates the prefixes stand for powers of
	ten so, for example, 28.8 kb/s means 28,800 bits per second.

	The unit is often dropped so one may talk of "a 40K salary"
	(40000 dollars) or "2 meg of disk space" (2*2^20 bytes).

	The accepted pronunciation of the initial G of "giga-" is
	hard, /gi'ga/.

	Confusing 1000 and 1024 (or other powers of 2 and 10 close in
	magnitude) - for example, describing a memory in units of 500K
	or 524K instead of 512K - is a sure sign of the {marketroid}.
	For example, 3.5" {microfloppies} are often described as
	storing "1.44 MB".  In fact, this is completely specious.  The
	correct size is 1440 KB = 1440 * 1024 = 1474560 bytes.  Alas,
	this point is probably lost on the world forever.

	In 1993, hacker Morgan Burke proposed, to general approval on
	{Usenet}, the following additional prefixes: groucho (10^-30),
	harpo (10^-27), harpi (10^27), grouchi (10^30).  This would
	leave the prefixes zeppo-, gummo-, and chico- available for
	future expansion.  Sadly, there is little immediate prospect
	that Mr. Burke's eminently sensible proposal will be ratified.

	2. <language> Related to the {prefix notation}.

	(2003-05-06)

<file system> An element of data storage in a {file system}.

	The history of computing is rich in varied kinds of files and
	{file systems}, whether ornate (e.g., {Macintosh file system}
	for a well-known case) or deficient (e.g., many simple
	pre-1980s file systems don't allow {directories}).

	However, the prototypical file has these characteristics:

	* It is a single sequence of bytes (but consider {Macintosh}
	{resource forks}).

	* It has a finite length, unlike, e.g. a {Unix} {device}.

	* It is stored in a {non-volatile storage} medium (but see
	{ramdrive}).

	* It exists (nominally) in a {directory}.

	* It has a name that it can be referred to by in file
	operations, possibly in combination with its {path}.

	Additionally, a file system may associate other information
	with a file, such as {permission} bits or other {file
	attributes}; timestamps for file creation, last revision, and
	last access; revision numbers (a` la VMS), and other kinds of
	{magic}.

	Compare: {document}.

	(1997-04-08)

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)

[probably from "main store"] In some varieties of Commonwealth
	hackish, the preferred synonym for {core}.  Thus, "bringing a
	program into store" means not that one is returning
	shrink-wrapped software but that a program is being {swap}ped
	in.

	[{Jargon File}]