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}.

<programming> A sequence of {data} values, usually {bytes},
	which usually stand for {characters} (a "character string").
	The {mapping} between values and characters is determined by
	the {character set} which is itself specified implcitly or
	explicitly by the environment in which the string is being
	interpreted.

	The most common character set is {ASCII} but, since the late
	1990s, there has been increased interest in larger character
	sets such as {Unicode} where each character is represented by
	more than eight {bits}.

	Most programming languages consider strings (e.g.
	"124:shabooya:\n", "hello world") basically distinct from
	numbers which are typically stored in fixed-length {binary} or
	{floating-point} representation.

	A {bit string} is a sequence of {bits}.

	(1999-12-21)

<jargon> A {marketroid} term for something he wants to sell
	you without bothering you with the often dizzying distinctions
	between {hardware}, {software}, {services}, {applications},
	{file formats}, companies, brand names and {operating
	systems}.

	"{Flash} is a perfect image-streaming solution."  "What is
	it?"  "Um...  about a thousand dollars."

	See also: {technology}.

	(1998-07-07)

1. <networking> A computer connected to a {network}.

	The term {node} includes devices such as routers and printers
	which would not normally be called "hosts".

	2. <communications> A computer to which one connects using a
	{terminal emulator}.

	(1995-02-16)

<unit> (b) {binary} digit.

	The unit of information; the amount of information obtained by
	asking a yes-or-no question; a computational quantity that can
	take on one of two values, such as false and true or 0 and 1;
	the smallest unit of storage - sufficient to hold one bit.

	A bit is said to be "set" if its value is true or 1, and
	"reset" or "clear" if its value is false or 0.  One speaks of
	setting and clearing bits.  To {toggle} or "invert" a bit is
	to change it, either from 0 to 1 or from 1 to 0.

	The term "bit" first appeared in print in the computer-science
	sense in 1949, and seems to have been coined by the eminent
	statistician, {John Tukey}.  Tukey records that it evolved
	over a lunch table as a handier alternative to "bigit" or
	"binit".

	See also {flag}, {trit}, {mode bit}, {byte}, {word}.

	[{Jargon File}]

	(2002-01-22)

1. Generalisation; ignoring or hiding details to capture some
	kind of commonality between different instances.  Examples are
	{abstract data types} (the representation details are hidden),
	{abstract syntax} (the details of the {concrete syntax} are
	ignored), {abstract interpretation} (details are ignored to
	analyse specific properties).

	2. <programming> Parameterisation, making something a function
	of something else.  Examples are {lambda abstractions} (making
	a term into a function of some variable), {higher-order
	functions} (parameters are functions), {bracket abstraction}
	(making a term into a function of a variable).

	Opposite of {concretisation}.

	(1998-06-04)

The process of analysis, design, coding and testing software.