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)

<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)

<operating system> /*'l*rt/ An audible and/or visual message
	intended to inform a system's users or administrators about a
	change in the operating conditions of that system or about
	some kind of error condition.  In a {graphical user
	interface}, an alert would typically be displayed as a small
	window containing the message and a button to click to dismiss
	the window.

	(1999-03-29)

<data> A data structure holding many values, possibly of
	different types, which is usually accessed sequentially,
	working from the head to the end of the tail - an "ordered
	list".  This contrasts with a (one-dimensional) {array}, any
	element of which can be accessed equally quickly.

	Lists are often stored using a cell and pointer arrangement
	where each value is stored in a cell along with an associated
	pointer to the next cell.  A special pointer, e.g. zero, marks
	the end of the list.  This is known as a (singly) "linked
	list".  A doubly linked list has pointers from each cell to
	both next and previous cells.

	An unordered list is a {set}.

	(1998-11-12)

<programming> A computer system or process that requests a
	service of another computer system or process (a "{server}")
	using some kind of {protocol} and accepts the server's
	responses.  A client is part of a {client-server} software
	architecture.

	For example, a {workstation} requesting the contents of a file
	from a {file server} is a client of the file server.

	(1997-10-27)

<messaging, open source> A complete {free}, {open-source}
	{e-mail client} from the {Mozilla Foundation} and therefore a
	true code descendent of the e-mail code in {Netscape
	Navigator}.  The first non-{beta release} was in late 2004.
	The {Firefox} web browser is from the same source.

	{Thunderbird Home
	(http://www.mozilla.org/products/thunderbird)}.

	(2005-01-26)

1. (Originally {Unix}, now also {MS-DOS}) A program that
	processes an input data stream into an output data stream in
	some well-defined way, and does no I/O to anywhere else except
	possibly on error conditions; one designed to be used as a
	stage in a {pipeline} (see {plumbing}).  Compare {sponge}.

	2. ({functional programming}) A {higher-order function} which
	takes a {predicate} and a list and returns those elements of
	the list for which the predicate is true.  In {Haskell}:

		filter p []     = []
		filter p (x:xs) = if p x then x : rest else rest
				  where
				  rest = filter p xs

	See also {filter promotion}.

	[{Jargon File}]

<operating system> A {directory} in the sense of a collection
	of computer {files}.  The term is more common in systems such
	as the {Macintosh} or {Windows 95} which have a {graphical
	user interface} and provide a graphical {file browser} in
	which directories are traditionally depicted as folders (like
	small briefcases).

	(1997-03-20)