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)

1. <storage> {DRAM refresh}.

	2. <hardware> {screen refresh}.

	(1998-10-19)

1. <messaging> (From Hormel's Spiced Ham, via the Monty Python
	"Spam" song) To post irrelevant or inappropriate messages to
	one or more {Usenet} {newsgroups}, {mailing lists}, or other
	messaging system in deliberate or accidental violation of
	{netiquette}.

	It is possible to spam a newsgroup with one well- (or ill-)
	planned message, e.g. asking "What do you think of abortion?"
	on soc.women.  This can be done by {cross-post}ing, e.g. any
	message which is crossposted to alt.rush-limbaugh and
	alt.politics.homosexuality will almost inevitably spam both
	groups.  (Compare {troll} and {flame bait}).

	Posting a message to a significant proportion of all
	newsgroups is a sure way to spam Usenet and become an object
	of almost universal hatred.  Canter and Siegel spammed the net
	with their Green card post.

	If you see an article which you think is a deliberate spam, DO
	NOT post a {follow-up} - doing so will only contribute to the
	general annoyance.  Send a polite message to the poster by
	private e-mail and CC it to "postmaster" at the same address.
	Bear in mind that the posting's origin might have been forged
	or the apparent sender's account might have been used by
	someone else without his permission.

	The word was coined as the winning entry in a 1937 competition
	to choose a name for Hormel Foods Corporation's "spiced meat"
	(now officially known as "SPAM luncheon meat").  Correspondant
	Bob White claims the modern use of the term predates Monty
	Python by at least ten years.  He cites an editor for the
	Dallas Times Herald describing Public Relations as "throwing a
	can of spam into an electric fan just to see if any of it
	would stick to the unwary passersby."

	{Usenet} newsgroup: {news:news.admin.net-abuse}.

	See also {netiquette}.

	2. (A narrowing of sense 1, above) To indiscriminately send
	large amounts of unsolicited {e-mail} meant to promote a
	product or service.  Spam in this sense is sort of like the
	electronic equivalent of junk mail sent to "Occupant".

	In the 1990s, with the rise in commercial awareness of the
	net, there are actually scumbags who offer spamming as a
	"service" to companies wishing to advertise on the net.  They
	do this by mailing to collections of {e-mail} addresses,
	Usenet news, or mailing lists.  Such practises have caused
	outrage and aggressive reaction by many net users against the
	individuals concerned.

	3. (Apparently a generalisation of sense 2, above) To abuse
	any network service or tool by for promotional purposes.

	"AltaVista is an {index}, not a promotional tool.  Attempts to
	fill it with promotional material lower the value of the index
	for everyone.  [...] We will disallow {URL} submissions from
	those who spam the index.  In extreme cases, we will exclude
	all their pages from the index." -- {Altavista}.

	4. <jargon, programming> To crash a program by overrunning a
	fixed-size {buffer} with excessively large input data.

	See also {buffer overflow}, {overrun screw}, {smash the stack}.

	5. <chat, games> (A narrowing of sense 1, above) To flood any
	{chat} forum or {Internet game} with purposefully annoying
	text or macros.  Compare {Scrolling}.

	(2003-09-21)

<messaging> 1. {electronic mail}.

	2. The {Berkeley Unix} program for composing and reading
	{electronic mail}.  It normally uses {sendmail} to handle
	delivery.

	{Unix manual page}: mail(1)

	(1997-12-03)