<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)

1. <database> See {data dictionary}.

	2. <programming> The core of a {CASE} tool, typically a {DBMS}
	where all development documents are stored.

	(1999-04-27)

1. <programming> To put something onto a {stack} or {pdl}.

	Opposite: "{pop}".

	2. <communications> {push media}.

	[{Jargon File}]

	(1997-04-10)

<storage> 1. {magnetic disk}.

	2. {compact disc}.

	3. {optical disk}.

	Note: the american spelling, "disk", is normal for most
	computer disks whereas "compact disc", having come to
	computers via the audio world, is correctly spelled with a
	"c", indeed, this spelling is part of the CD standard.

	(1995-07-30)

<programming> An unwanted and unintended property of a program
	or piece of hardware, especially one that causes it to
	malfunction.  Antonym of {feature}.  E.g. "There's a bug in
	the editor: it writes things out backward."  The
	identification and removal of bugs in a program is called
	"{debugging}".

	Admiral {Grace Hopper} (an early computing pioneer better
	known for inventing {COBOL}) liked to tell a story in which a
	technician solved a {glitch} in the {Harvard Mark II machine}
	by pulling an actual insect out from between the contacts of
	one of its relays, and she subsequently promulgated {bug} in
	its hackish sense as a joke about the incident (though, as she
	was careful to admit, she was not there when it happened).
	For many years the logbook associated with the incident and
	the actual bug in question (a moth) sat in a display case at
	the Naval Surface Warfare Center (NSWC).  The entire story,
	with a picture of the logbook and the moth taped into it, is
	recorded in the "Annals of the History of Computing", Vol. 3,
	No. 3 (July 1981), pp. 285--286.

	The text of the log entry (from September 9, 1947), reads
	"1545 Relay #70 Panel F (moth) in relay.  First actual case of
	bug being found".  This wording establishes that the term was
	already in use at the time in its current specific sense - and
	Hopper herself reports that the term "bug" was regularly
	applied to problems in radar electronics during WWII.

	Indeed, the use of "bug" to mean an industrial defect was
	already established in Thomas Edison's time, and a more
	specific and rather modern use can be found in an electrical
	handbook from 1896 ("Hawkin's New Catechism of Electricity",
	Theo. Audel & Co.)  which says: "The term "bug" is used to a
	limited extent to designate any fault or trouble in the
	connections or working of electric apparatus."  It further
	notes that the term is "said to have originated in
	{quadruplex} telegraphy and have been transferred to all
	electric apparatus."

	The latter observation may explain a common folk etymology of
	the term; that it came from telephone company usage, in which
	"bugs in a telephone cable" were blamed for noisy lines.
	Though this derivation seems to be mistaken, it may well be a
	distorted memory of a joke first current among *telegraph*
	operators more than a century ago!

	Actually, use of "bug" in the general sense of a disruptive
	event goes back to Shakespeare!  In the first edition of
	Samuel Johnson's dictionary one meaning of "bug" is "A
	frightful object; a walking spectre"; this is traced to
	"bugbear", a Welsh term for a variety of mythological monster
	which (to complete the circle) has recently been reintroduced
	into the popular lexicon through fantasy {role-playing games}.

	In any case, in jargon the word almost never refers to
	insects.  Here is a plausible conversation that never actually
	happened:

	"There is a bug in this ant farm!"

	"What do you mean?  I don't see any ants in it."

	"That's the bug."

	[There has been a widespread myth that the original bug was
	moved to the Smithsonian, and an earlier version of this entry
	so asserted.  A correspondent who thought to check discovered
	that the bug was not there.  While investigating this in late
	1990, your editor discovered that the NSWC still had the bug,
	but had unsuccessfully tried to get the Smithsonian to accept
	it - and that the present curator of their History of
	American Technology Museum didn't know this and agreed that it
	would make a worthwhile exhibit.  It was moved to the
	Smithsonian in mid-1991, but due to space and money
	constraints has not yet been exhibited.  Thus, the process of
	investigating the original-computer-bug bug fixed it in an
	entirely unexpected way, by making the myth true!  - ESR]

	[{Jargon File}]

	(1999-06-29)

<data, database, programming> An {ordered set} of {fields},
	usually stored contiguously.  The term is used with similar
	meaning in several different contexts.  In a file, a "record"
	probably has some fixed length, in contrast to a "line" which
	may have any length and is terminated by some {End Of Line}
	sequence).  A {database} record is also called a "row".  In a
	{spreadsheet} it is always called a "row".  Some programming
	languages use the term to mean a type composed of fields of
	several other types ({C} calls this a "{struct}").

	In all these cases, a record represents an entity with certain
	field values.

	Fields may be of a fixed width ({bits} or {characters}) or
	they may be separated by a {delimiter} character, often
	{comma} ({CSV}) or {HT} ({TSV}).

	In a database the list of values of a given field from all
	records is called a column.

	(2002-03-22)

<tool> A dyslexic acronym for "A Yacc-like Haskell Parser
	generator".

	An {LALR1 grammar} {parser generator} for {Haskell}.  Happy is
	written in Haskell, uses a parser generated by itself, and can
	be compiled using {ghc}, {hbc} or {gofer}.  Happy uses an
	implementation of {monadic IO} built on top of stream IO, but
	this should change when the {Haskell 1.3} {standard} has been
	implemented.

	Version: 0.9 (1996-02-28).

	Happy is covered by the {General Public License}.

	{Home (http://www.dcs.gla.ac.uk/fp/software/happy.html)}.

	{(ftp://ftp.dcs.gla.ac.uk/pub/haskell/happy/)}.

	E-mail: <andy@dcs.gla.ac.uk>, <simonm@dcs.gla.ac.uk>.

	(1996-03-21)

<hardware> To press and release a {button} on a {mouse} or
	other {pointing device}.  This generates an {event}, also
	specifying the screen position, which is processed by the
	{window manager} or {application program}.  On a mouse with
	more than one button, the unqualified term usually implies
	pressing the left-most button (with the right index finger),
	other buttons would be qualified, e.g. "{right-click}".
	{Keyboard} modifiers may also be used, e.g. "shift-click",
	meaning to hold down the shift key on the keyboard while
	clicking the mouse button.

	If the mouse moves while the button is pressed then this is a
	{drag}.

	(1995-03-14)

1. <file system> {hard link} or {symbolic link}.

	2. <hypertext> {hyperlink}.

	(1997-10-22)

<programming> To process a {node} while {traversing} a
	{graph}.

	(2001-09-30)

1. One of a small number of high-speed memory locations in a
	computer's {CPU}.  Registers differ from ordinary
	{random access memory} in several respects:

	There are only a small number of registers (the "register
	set"), typically 32 in a modern processor though some,
	e.g. {SPARC}, have as many as 144.  A register may be directly
	addressed with a few bits.  In contrast, there are usually
	millions of words of main memory (RAM), requiring at least
	twenty bits to specify a memory location.  Main memory
	locations are often specified indirectly, using an {indirect
	addressing} mode where the actual memory address is held in a
	register.

	Registers are fast; typically, two registers can be read and a
	third written -- all in a single cycle.  Memory is slower; a
	single access can require several cycles.

	The limited size and high speed of the register set makes it
	one of the critical resources in most computer architectures.
	{Register allocation}, typically one phase of the {back-end},
	controls the use of registers by a compiled program.

	See also {accumulator}, {FUBAR}, {orthogonal}, {register
	dancing}, {register allocation}, {register spilling}.

	2. An addressable location in a {memory-mapped} peripheral
	device.  E.g. the transmit data register in a {UART}.