<messaging> One of {Usenet}'s huge collection of topic groups
	or {fora}.  {Usenet} groups can be "unmoderated" (anyone can
	post) or "moderated" (submissions are automatically directed
	to a {moderator}, who edits or filters and then posts the
	results).  Some newsgroups have parallel {mailing lists} for
	{Internet} people with no netnews access, with postings to the
	group automatically propagated to the list and vice versa.
	Some moderated groups (especially those which are actually
	gatewayed {Internet} {mailing lists}) are distributed as
	"{digests}", with groups of postings periodically collected
	into a single large posting with an index.

	Among the best-known are comp.lang.c (the {C}-language forum),
	comp.arch (on computer architectures), comp.Unix.wizards (for
	{Unix wizards}), rec.arts.sf-lovers (for science-fiction
	fans), and talk.politics.misc (miscellaneous political
	discussions and {flamage}).

	Barry Shein <bzs@world.std.com> is alleged to have said,
	"Remember the good old days when you could read all the group
	names in one day?"  This gives a good idea of the growth and
	size of {Usenet}.

	See also {netiquette}.

	[{Jargon File}]

	(1994-12-13)

<operating system> ("back up" when used as a verb) A spare
	copy of a file, file system, or other resource for use in the
	event of failure or loss of the original.

	The term commonly refers to a copy of the files on a
	computer's {disks}, made periodically and kept on {magnetic
	tape} or other removable medium (also called a "{dump}").

	This essential precaution is neglected by most new computer
	users until the first time they experience a {disk crash} or
	accidentally delete the only copy of the file they have been
	working on for the last six months.  Ideally the backup copies
	should be kept at a different site or in a fire safe since,
	though your hardware may be insured against fire, the data on
	it is almost certainly neither insured nor easily replaced.

	See also {backup software}, {differential backup},
	{incremental backup}, {full backup}.  Compare {archive},
	{source code management}.

	(2004-03-16)

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)

/sink/ (Or "synch") 1. To synchronise, to bring into
	synchronisation.

	2. <file system> To force ("{flush}") all pending buffered
	disk writes to the disk.

	3. More generally, to force a number of competing processes or
	agents to a state that would be "safe" if the system were to
	crash, i.e. to {checkpoint} in the {database} sense.

	[{Jargon File}]

	(1994-11-11)

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)

<jargon> Said of anything that is or causes a {lose} or
	{lossage}.

	[{Jargon File}]

<database, networking> Creating and maintaining a duplicate
	copy of a database or file system on a different computer,
	typically a {server}.  The term usually implies the
	intelligent copying of parts of the source database which have
	changed since the last replication with the destination.

	Replication may be one-way or two-way.  Two-way replication is
	much more complicated because of the possibility that a
	replicated object may have been updated differently in the two
	locations in which case some method is needed to reconcile the
	different versions.

	For example, {Lotus Notes} can automatically distribute
	document databases across telecommunications networks.  Notes
	supports a wide range of network {protocols} including {X25}
	and {Internet} {TCP/IP}.

	Compare {mirror}.  See also {rdist}.

	(1997-12-12)

<chat> The owner of a {bot}.

	(1997-04-07)

1. <mathematics> {Base} two.  A number representation
	consisting of zeros and ones used by practically all computers
	because of its ease of implementation using digital
	electronics and {Boolean algebra}.

	2. <file format> {binary file}.

	3. <programming> A description of an {operator} which takes
	two {arguments}.  See also {unary}, {ternary}.

	(2005-02-21)

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)

See {followup}.

1. <operating system> (Or "erase") To make a file
	inaccessible.

	Usually this operation only deletes information from the
	tables the {file system} uses to locate named files; the
	file's contents still exist on {disk} and can sometimes be
	recovered by scanning the whole disk for strings which are
	known to have been in the file.  Files created subsequently on
	the same disk are quite likely to reuse the same blocks and
	thus overwrite the deleted file's data permanently.

	2. <character> The {control character} with {ASCII} code 127.
	Usually entering this character from the keyboard deletes the
	last character typed from the {input buffer}.  Sadly there is
	great confusion between {operating systems} and keyboard
	manufacturers as to whether this function should be assigned
	to the delete or {backspace} key/character.

	The choice of code 127 (binary 1111111) is not arbitrary but
	dates back to the use of {paper tape} for input.  The delete
	key rewound the tape by one character and punched out all
	seven holes, thus obliterating whatever character was there
	before.  The tape reading software ignored any delete
	characters in the input.

	(1996-12-01)