<operating system> See {Microsoft Windows}, {Windows NT}.

	(1997-11-23)

1. {Netscape Navigator}.

	2. {Netscape Communications Corporation}.

The structure of strings in some language.  A language's
	syntax is described by a {grammar}.  For example, the syntax
	of a binary number could be expressed as

		binary_number = bit [ binary_number ]

		bit = "0" | "1"

	meaning that a binary number is a bit optionally followed by a
	binary number and a bit is a literal zero or one digit.

	The meaning of the language is given by its {semantics}.

	See also {abstract syntax}, {concrete syntax}.

	(1994-10-31)

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)

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)

<language, text> An {SGML}, {HTML}, or {XML} {token}
	representing the beginning (start tag: "<p ...>") or end (end
	tag: "</p>") of an {element}.  In normal SGML {syntax} (and
	always in {XML}), a tag starts with a "<" and ends with an
	">".

	In {HTML} jargon, the term "tag" is often used for an
	"{element}".

	(2001-01-31)

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)

<operating system, programming> The ease with which a piece of
	software (or {file format}) can be "ported", i.e. made to run
	on a new {platform} and/or compile with a new {compiler}.

	The most important factor is the language in which the
	software is written and the most portable language is almost
	certainly {C} (though see {Vaxocentrism} for counterexamples).
	This is true in the sense that C compilers are available for
	most systems and are often the first compiler provided for a
	new system.  This has led several compiler writers to compile
	other languages to C code in order to benefit from its
	portability (as well as the quality of compilers available for
	it).

	The least portable type of language is obviously {assembly
	code} since it is specific to one particular (family of)
	{processor}(s).  It may be possible to translate mechanically
	from one assembly code (or even {machine code}) into another
	but this is not really portability.  At the other end of the
	scale would come {interpreted} or {semi-compiled} languages
	such as {LISP} or {Java} which rely on the availability of a
	portable {interpreter} or {virtual machine} written in a lower
	level language (often C for the reasons outlined above).

	The act or result of porting a program is called a "port".
	E.g. "I've nearly finished the {Pentium} port of my big bang
	simulation."

	Portability is also an attribute of {file formats} and depends
	on their adherence to {standards} (e.g. {ISO 8859}) or the
	availability of the relevant "viewing" software for different
	{platforms} (e.g. {PDF}).

	(1997-06-18)

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)

<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)

1. See {multithreading}.

	2. See {threaded code}.

	3. {topic thread}.

	[{Jargon File}]

<library, networking> {Berkeley} {Unix} networking {socket}
	library routine to satisfy a connection request from a remote
	{host}.  A specified socket on the local host (which must be
	capable of accepting the connection) is connected to the
	requesting socket on the remote host.  The remote socket's
	socket address is returned.

	{Unix manual pages}: accept(2), connect(2).

	(1994-11-08)