<electronics> Part of a system output presented at its input.
	Feedback may be unintended.  When used as a design feature,
	the output is usually transformed by passive components which
	attenuate it in some manner; the result is then presented at
	the system input.

	Feedback is positive or negative, depending on the sign with
	which a positive change in the original input reappears after
	transformation.  Negative feedback was invented by Black to
	stabilise {vacuum tube} amplifiers.  The behaviour becomes
	largely a function of the feedback transformation and only
	minimally a function of factors such as transistor gain which
	are imperfectly known.

	Positive feedback can lead to instability; it finds wide
	application in the construction of oscillators.

	Feedback can be used to control a system, as in {feedback
	control}.

	(1996-01-02)

<computer> A range of home computers first released by
	{Commodore Business Machines} in early 1985 (though they did
	not design the original - see below).  Amigas were popular for
	{games}, {video processing}, and {multimedia}.  One notable
	feature is a hardware {blitter} for speeding up graphics
	operations on whole areas of the screen.

	The Amiga was originally called the Lorraine, and was
	developed by a company named "Amiga" or "Amiga, Inc.", funded
	by some doctors to produce a killer game machine.  After the
	US game machine market collapsed, the Amiga company sold some
	{joysticks} but no Lorraines or any other computer.  They
	eventually floundered and looked for a buyer.

	Commodore at that time bought the (mostly complete) Amiga
	machine, infused some money, and pushed it through the final
	stages of development in a hurry.  Commodore released it
	sometime[?] in 1985.

	Most components within the machine were known by nicknames.
	The {coprocessor} commonly called the "Copper" is in fact the
	"{Video} Timing Coprocessor" and is split between two chips:
	the instruction fetch and execute units are in the "Agnus"
	chip, and the {pixel} timing circuits are in the "Denise" chip
	(A for address, D for data).

	"Agnus" and "Denise" were responsible for effects timed to the
	{real-time} position of the video scan, such as midscreen
	{palette} changes, {sprite multiplying}, and {resolution}
	changes.  Different versions (in order) were: "Agnus" (could
	only address 512K of {video RAM}), "Fat Agnus" (in a {PLCC}
	package, could access 1MB of video RAM), "Super Agnus"
	(slightly upgraded "Fat Agnus").  "Agnus" and "Fat Agnus" came
	in {PAL} and {NTSC} versions, "Super Agnus" came in one
	version, jumper selectable for PAL or NTSC.  "Agnus" was
	replaced by "Alice" in the A4000 and A1200, which allowed for
	more {DMA} channels and higher bus {bandwidth}.

	"Denise" outputs binary video data (3*4 bits) to the "Vidiot".
	The "Vidiot" is a hybrid that combines and amplifies the
	12-bit video data from "Denise" into {RGB} to the {monitor}.

	Other chips were "Amber" (a "flicker fixer", used in the A3000
	and Commodore display enhancer for the A2000), "Gary" ({I/O},
	addressing, G for {glue logic}), "Buster" (the {bus
	controller}, which replaced "Gary" in the A2000), "Buster II"
	(for handling the Zorro II/III cards in the A3000, which meant
	that "Gary" was back again), "Ramsey" (The {RAM} controller),
	"DMAC" (The DMA controller chip for the WD33C93 {SCSI adaptor}
	used in the A3000 and on the A2091/A2092 SCSI adaptor card for
	the A2000; and to control the {CD-ROM} in the {CDTV}), and
	"Paula" ({Peripheral}, Audio, {UART}, {interrupt} Lines, and
	{bus Arbiter}).

	There were several Amiga chipsets: the "Old Chipset" (OCS),
	the "Enhanced Chipset" (ECS), and {AGA}.  OCS included
	"Paula", "Gary", "Denise", and "Agnus".

	ECS had the same "Paula", "Gary", "Agnus" (could address 2MB
	of Chip RAM), "Super Denise" (upgraded to support "Agnus" so
	that a few new {screen modes} were available).  With the
	introduction of the {Amiga A600} "Gary" was replaced with
	"Gayle" (though the chipset was still called ECS).  "Gayle"
	provided a number of improvments but the main one was support
	for the A600's {PCMCIA} port.

	The AGA chipset had "Agnus" with twice the speed and a 24-bit
	palette, maximum displayable: 8 bits (256 colours), although
	the famous "{HAM}" (Hold And Modify) trick allows pictures of
	256,000 colours to be displayed.  AGA's "Paula" and "Gayle"
	were unchanged but AGA "Denise" supported AGA "Agnus"'s new
	screen modes.  Unfortunately, even AGA "Paula" did not support
	High Density {floppy disk drives}.  (The Amiga 4000, though,
	did support high density drives.)  In order to use a high
	density disk drive Amiga HD floppy drives spin at half the
	rotational speed thus halving the data rate to "Paula".

	Commodore Business Machines went bankrupt on 1994-04-29,
	the German company {Escom AG} bought the rights to the Amiga
	on 1995-04-21 and the Commodore Amiga became the Escom
	Amiga.  In April 1996 Escom were reported to be making the
	{Amiga} range again but they too fell on hard times and
	{Gateway 2000} (now called Gateway) bought the Amiga brand
	on 1997-05-15.

	Gateway licensed the Amiga operating system to a German
	hardware company called {Phase 5} on 1998-03-09.  The
	following day, Phase 5 announced the introduction of a
	four-processor {PowerPC} based Amiga {clone} called the
	"{pre\box}".  Since then, it has been announced that the
	new operating system will be a version of {QNX}.

	On 1998-06-25, a company called {Access Innovations Ltd}
	announced {plans (http://www.micktinker.co.uk/aaplus.html)} to
	build a new Amiga chip set, the {AA+}, based partly on the AGA
	chips but with new fully 32-bit functional core and 16-bit AGA
	{hardware register emulation} for {backward compatibility}.
	The new core promised improved memory access and video display
	DMA.

	By the end of 2000, Amiga development was under the control of
	a [new?] company called {Amiga, Inc.}.  As well as continuing
	development of AmigaOS (version 3.9 released in December
	2000), their "Digital Environment" is a {virtual machine} for
	multiple {platforms} conforming to the {ZICO} specification.
	As of 2000, it ran on {MIPS}, {ARM}, {PPC}, and {x86}
	processors.

	{Home (http://www.amiga.com/)}.

	{Amiga Web Directory (http://www.cucug.org/amiga.html)}.

	{amiCrawler (http://www.amicrawler.com/)}.

	Newsgroups: {news:comp.binaries.amiga},
	{news:comp.sources.amiga}, {news:comp.sys.amiga},
	{news:comp.sys.amiga.advocacy},
	{news:comp.sys.amiga.announce},
	{news:comp.sys.amiga.applications},
	{news:comp.sys.amiga.audio}, {news:comp.sys.amiga.datacomm},
	{news:comp.sys.amiga.emulations}, {news:comp.sys.amiga.games},
	{news:comp.sys.amiga.graphics},
	{news:comp.sys.amiga.hardware},
	{news:comp.sys.amiga.introduction},
	{news:comp.sys.amiga.marketplace}, {news:comp.sys.amiga.misc},
	{news:comp.sys.amiga.multimedia},
	{news:comp.sys.amiga.programmer},
	{news:comp.sys.amiga.reviews}, {news:comp.sys.amiga.tech},
	{news:comp.sys.amiga.telecomm}, {news:comp.Unix.amiga}.

	See {aminet}, {Amoeba}, {bomb}, {exec}, {gronk}, {guru
	meditation}, {Intuition}, {sidecar}, {slap on the side},
	{Vulcan nerve pinch}.

	(2003-07-05)

1. {audio}.

	2. <logic> An {inference system} A is sound with respect to
	another system B if A can only reach conclusions which are
	true in B.  A {type inference} system is considered sound with
	respect to a {semantics} if the type inferred for an
	expression is the same as the type inferred for the meaning of
	that expression under the semantics.

	The dual to soundness is {complete}ness.

	(1995-03-01)

<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)

<jargon> ({MIT}) 1. To fail.  A program loses when it
	encounters an exceptional condition or fails to work in the
	expected manner.

	2. To be exceptionally unesthetic or crocky.

	3. Of people, to be obnoxious or unusually stupid (as opposed
	to ignorant).

	4. Refers to something that is {losing}, especially in the
	phrases "That's a lose!" and "What a lose!"

	[{Jargon File}]

	(1995-04-19)

1. The title page added to printouts by most {print spoolers}.
	Typically includes user or account ID information in very
	large character-graphics capitals.  Also called a "burst
	page", because it indicates where to burst (tear apart)
	fanfold paper to separate one user's printout from the next.

	2. A similar printout generated (typically on multiple pages
	of fan-fold paper) from user-specified text, e.g. by a program
	such as {Unix}'s "banner".

	3. {splash screen}.

	[{Jargon File}]

	(1994-11-28)