<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)

<parallel> Sharing a single {CPU} between multiple tasks (or
	"threads") in a way designed to minimise the time required to
	switch threads.  This is accomplished by sharing as much as
	possible of the program execution environment between the
	different threads so that very little state needs to be saved
	and restored when changing thread.

	Multithreading differs from {multitasking} in that threads
	share more of their environment with each other than do tasks
	under multitasking.  Threads may be distinguished only by the
	value of their {program counters} and {stack pointers} while
	sharing a single {address space} and set of {global
	variables}.  There is thus very little protection of one
	thread from another, in contrast to multitasking.

	Multithreading can thus be used for very fine-grain
	multitasking, at the level of a few instructions, and so can
	hide {latency} by keeping the processor busy after one thread
	issues a long-latency instruction on which subsequent
	instructions in that thread depend.

	A {light-weight process} is somewhere between a thread and a
	full process.

	{TL0} is an example of a threaded machine language.
	{Dataflow} computation (E.g. {Id} and {SISAL}) is an extreme
	form of multithreading.

	(1997-12-23)

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)

/knooth/ 1. {Donald Knuth}.

	2. ["The Art of Computer Programming", Donald E. Knuth]
	Mythically, the reference that answers all questions about
	data structures or algorithms.  A safe answer when you do not
	know: "I think you can find that in Knuth."

	Contrast {literature}.  See also {bible}.

	[{Jargon File}]

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)