1. <hardware> {monitor}.

	2. <language> A vector of pointers to {activation records}.
	The Nth element points to the activation record containing
	variables declared at {lexical depth} N.  This allows faster
	access to variables from outer {scopes} than the alternative
	of linked activation records (but most variable accesses are
	either local or global or occasionally to the immediately
	enclosing scope).  Displays were used in some {ALGOL}
	implementations.

	(1996-02-22)

<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)

<data, database> An area of a {database} {record}, or
	{graphical user interface} {form}, into which a particular
	item of data is entered.

	Example usage: "The telephone number field is not really a
	numerical field", "Why do we need a four-digit field for the
	year?".

	A {database} {column} is the set of all instances of a given
	field from all records in a {table}.

	(1999-04-26)

1. <networking> A {bang path} or explicitly routed {Internet
	address}; a node-by-node specification of a link between two
	machines.

	2. <file system> {pathname}.

	3. <operating system>  The list of directories the kernel
	(under {Unix}) or the command interpreter (under {MS-DOS})
	searches for {executables}.  It is stored as part of the
	{environment} in both operating systems.

	Other, similar constructs abound under Unix; the {C}
	{preprocessor}, for example, uses such a search path to locate
	"#include" files.

	[{Jargon File}]

	(1996-11-21)

<data, data processing, jargon> /day't*/ (Or "raw data")
	Numbers, {characters}, {images}, or other method of recording,
	in a form which can be assessed by a human or (especially)
	input into a {computer}, stored and {processed} there, or
	transmitted on some {digital channel}.  Computers nearly
	always represent data in {binary}.

	Data on its own has no meaning, only when interpreted by some
	kind of {data processing system} does it take on meaning and
	become {information}.

	People or computers can find patterns in data to perceive
	information, and information can be used to enhance
	{knowledge}.  Since knowledge is prerequisite to wisdom, we
	always want more data and information.  But, as modern
	societies verge on {information overload}, we especially need
	better ways to find patterns.

	1234567.89 is data.

	"Your bank balance has jumped 8087% to $1234567.89" is
	information.

	"Nobody owes me that much money" is knowledge.

	"I'd better talk to the bank before I spend it, because of
	what has happened to other people" is wisdom.

	(1999-04-30)

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)

<theory> A category K is a collection of objects, obj(K), and
	a collection of {morphisms} (or "{arrows}"), mor(K) such that

	1. Each morphism f has a "typing" on a pair of objects A, B
	written f:A->B.  This is read 'f is a morphism from A to B'.
	A is the "source" or "{domain}" of f and B is its "target" or
	"{co-domain}".

	2. There is a {partial function} on morphisms called
	{composition} and denoted by an {infix} ring symbol, o.  We
	may form the "composite" g o f : A -> C if we have g:B->C and
	f:A->B.

	3. This composition is associative: h o (g o f) = (h o g) o f.

	4. Each object A has an identity morphism id_A:A->A associated
	with it.  This is the identity under composition, shown by the
	equations id_B o f = f = f o id_A.

	In general, the morphisms between two objects need not form a
	{set} (to avoid problems with {Russell's paradox}).  An
	example of a category is the collection of sets where the
	objects are sets and the morphisms are functions.

	Sometimes the composition ring is omitted.  The use of
	capitals for objects and lower case letters for morphisms is
	widespread but not universal.  Variables which refer to
	categories themselves are usually written in a script font.

	(1997-10-06)

<computer> 1. A computer; especially in the construction "foo
	box" where foo is some functional qualifier, like "graphics",
	or the name of an {operating system} (thus, "{Unix} box",
	"{MS-DOS} box", etc.)  "We preprocess the data on Unix boxes
	before handing it up to the {mainframe}."  The plural
	"{boxen}" is sometimes seen.

	2. Without qualification in an {IBM} {SNA} site, "box" refers
	specifically to an {IBM} {front-end processor}.

	[{Jargon File}]

	(1994-11-29)