1. The operator's station of a {mainframe}.  In times past,
	this was a privileged location that conveyed godlike powers to
	anyone with fingers on its keys.  Under {Unix} and other
	modern {time-sharing} {operating systems}, such privileges are
	guarded by passwords instead, and the console is just the
	{tty} the system was booted from.  Some of the mystique
	remains, however, and it is traditional for {sysadmins} to
	post urgent messages to all users from the console (on Unix,
	/dev/console).

	2. On {microcomputer} {Unix} boxes, the main screen and
	keyboard (as opposed to character-only terminals talking to a
	{serial port}).  Typically only the console can do real
	graphics or run {X}.  See also {CTY}.

	[{Jargon File}]

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)

1. <mathematics> A collection of {nodes} and {edges}.

	See also {connected graph}, {degree}, {directed graph}, {Moore
	bound}, {regular graph}, {tree}.

	2. <graphics> A visual representation of algebraic equations
	or data.

	(1996-09-22)

1. To cause to be {broken} (in any sense).  "Your latest patch
	to the editor broke the paragraph commands."

	2. (Of a program) To stop temporarily, so that it may
	debugged.  The place where it stops is a "{breakpoint}".

	3. To send an {EIA-232} break (two character widths of line
	high) over a {serial line}.

	4. [Unix] To strike whatever key currently causes the tty
	driver to send SIGINT to the current process.  Normally,
	break, delete or {control-C} does this.

	5. "break break" may be said to interrupt a conversation (this
	is an example of verb doubling).  This usage comes from radio
	communications, which in turn probably came from landline
	telegraph/teleprinter usage, as badly abused in the Citizen's
	Band craze a few years ago.

	6. {pipeline break}.

	7. {break statement}.

	[{Jargon File}]

	(2004-03-24)

1. <file format> A single file containing one or (usually)
	more separate files plus information to allow them to be
	extracted (separated) by a suitable program.

	Archives are usually created for software distribution or
	{backup}.  {tar} is a common format for {Unix} archives, and
	{arc} or {PKZIP} for {MS-DOS} and {Microsoft Windows}.

	2. <operating system> To transfer files to slower, cheaper
	media (usually {magnetic tape}) to free the {hard disk} space
	they occupied.  This is now normally done for long-term
	storage but in the 1960s, when disk was much more expensive,
	files were often shuffled regularly between disk and tape.

	3. <networking> {archive site}.

	(1996-12-08)

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)

See {followup}.

<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)

<software> 1. A temporary addition to a piece of code, usually
	as a {quick-and-dirty} remedy to an existing {bug} or
	{misfeature}.  A patch may or may not work, and may or may not
	eventually be incorporated permanently into the program.
	Distinguished from a {diff} or {mod} by the fact that a patch
	is generated by more primitive means than the rest of the
	program; the classical examples are instructions modified by
	using the front panel switches, and changes made directly to
	the binary executable of a program originally written in an
	{HLL}.  Compare {one-line fix}.

	2. To insert a patch into a piece of code.

	3. [in the Unix world] A {diff}.

	4. A set of modifications to binaries to be applied by a
	patching program.  {IBM} systems often receive updates to the
	{operating system} in the form of absolute {hexadecimal}
	patches.  If you have modified your OS, you have to
	disassemble these back to the {source code}.  The patches
	might later be corrected by other patches on top of them
	(patches were said to "grow scar tissue").  The result was
	often a convoluted {patch space} and headaches galore.

	There is a classic story of a {tiger team} penetrating a
	secure military computer that illustrates the danger inherent
	in binary patches (or, indeed, any patches that you can't - or
	don't - inspect and examine before installing).  They couldn't
	find any {trap doors} or any way to penetrate security of
	IBM's OS, so they made a site visit to an IBM office
	(remember, these were official military types who were
	purportedly on official business), swiped some IBM stationery,
	and created a fake patch.  The patch was actually the trapdoor
	they needed.  The patch was distributed at about the right
	time for an IBM patch, had official stationery and all
	accompanying documentation, and was dutifully installed.  The
	installation manager very shortly thereafter learned something
	about proper procedures.

	5. {Larry Wall}'s "patch" utility, which automatically applies
	a patch to a set of {source code} or other text files.  Patch
	accepts input in any of the four forms output by the {Unix}
	{diff} utility.  When the files being patched are not
	identical to those on which the diffs were based, patch uses
	{heuristics} to determine how to proceed.

	Diff and patch are the standard way of producing and applying
	updates under {Unix}.  Both have been ported to other
	{operating systems}.

	{Patch Home (http://www.gnu.org/software/patch/patch.html)}.

	[{Jargon File}]

	(2005-05-16)

1. <operating system> The {Unix} {superuser} account (with
	user name "root" and user ID 0) that overrides file
	permissions.  The term {avatar} is also used.  By extension,
	the privileged system-maintenance login on any {operating
	system}.

	See {root mode}, {go root}, {wheel}.

	[{Jargon File}]

	(1994-10-27)

	2. <operating system> {root directory}.

	(1996-11-21)

	3. <data> {root node}.

	(1998-11-14)

<mathematics> (Or "whole number") One of the {finite} numbers
	in the infinite set

		..., -3, -2, -1, 0, 1, 2, 3, ...

	An {inductive definition} of an integer is a number that is
	either zero or an integer plus or minus one.  An integer is a
	number with no fractional part.  If written as a {fixed-point}
	number, the part after the decimal (or other base) point will
	be zero.

	A {natural number} is a non-negative integer.

	(2002-04-07)

<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)

<World-Wide Web, project> A {open source} {HTTP} server for
	{Unix}, {Windows NT}, and other {platforms}.  Apache was
	developed in early 1995, based on code and ideas found in the
	most popular HTTP server of the time, {NCSA httpd} 1.3.  It
	has since evolved to rival (and probably surpass) almost any
	other {Unix} based HTTP server in terms of functionality, and
	speed.  Since April 1996 Apache has been the most popular HTTP
	server on the {Internet}, in May 1999 it was running on 57% of
	all web servers.

	It features highly configurable error messages, {DBM}-based
	{authentication} {databases}, and {content negotiation}.

	Latest version: 1.3.9, as of 1999-10-27.

	{Home (http://www.apache.org/httpd.html)}.

	{FAQ (http://www.apache.org/docs/misc/FAQ.html)}.

	(1999-10-27)

<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. Not operating.  "The up escalator is down" is considered a
	humorous thing to say, and "The elevator is down" always
	means "The elevator isn't working" and never refers to what
	floor the elevator is on.  With respect to computers, this
	term has passed into the mainstream; the extension to other
	kinds of machine is still hackish.

	2. "go down" To stop functioning; usually said of the
	{system}.  The message from the {console} that every hacker
	hates to hear from the operator is "System going down in 5
	minutes".

	3. "take down", "bring down" To deactivate purposely, usually
	for repair work or {PM}.  "I'm taking the system down to work
	on that bug in the tape drive."  Occasionally one hears the
	word "down" by itself used as a verb in this sense.

	See {crash}; opposite: {up}.

	[{Jargon File}]

	(1994-12-07)

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> A {release} of a piece of software which is not
	a {major release} or a {bugfix}, but only introduces small
	changes or new features.

	(1996-08-04)

<computer> 1. A computer; especially in the construction "foo
	box" where foo is some functional qualifier, like "graphics",
	or the name of an {operating system} (thus, "{Unix} box",
	"{MS-DOS} box", etc.)  "We preprocess the data on Unix boxes
	before handing it up to the {mainframe}."  The plural
	"{boxen}" is sometimes seen.

	2. Without qualification in an {IBM} {SNA} site, "box" refers
	specifically to an {IBM} {front-end processor}.

	[{Jargon File}]

	(1994-11-29)