A group G is a non-empty {set} upon which a {binary} operator
	* is defined with the following properties for all a,b,c in G:

	  Closure:     G is closed under *,  a*b in G
	  Associative: * is associative on G, (a*b)*c = a*(b*c)
	  Identity:    There is an identity element  e  such that
		       a*e = e*a = a.
	  Inverse:     Every element has a unique inverse a' such that
		       a * a' = a' * a = e.  The inverse is usually
		       written with a superscript -1.

	(1998-10-03)

<convention, data> A string unique to a time duration of 24
	hours between 2 successive midnights defined by the local time
	zone.  The specific representation of a date will depend on
	which calendar convention is in force; e.g., Gregorian,
	Islamic, Japanese, Chinese, Hebrew etc. as well as local
	ordering conventions such as UK: day/month/year, US:
	month/day/year.

	Inputting and outputting dates on computers is greatly
	complicated by these {localisation} issues which is why they
	tend to operate on dates internally in some unified form such
	as seconds past midnight at the start of the first of January
	1970.

	Many software and hardware representations of dates allow only
	two digits for the year, leading to the {year 2000} problem.

	{Unix manual page}: date(1), ctime(3).

	(1997-07-11)

<electronics> The quantity of {charge} per unit time, measured
	in Amperes (Amps, A).  By historical convention, the sign of
	current is positive for currents flowing from positive to
	negative {potential}, but experience indicates that electrons
	are negatively charged and flow in the opposite direction.

	(1995-10-05)

1. <theory> In {domain theory}, the sum A + B of two {domains}
	contains all elements of both domains, modified to indicate
	which part of the union they come from, plus a new {bottom}
	element.  There are two constructor functions associated with
	the sum:

		inA : A -> A+B       inB : B -> A+B
		inA(a) = (0,a)	     inB(b) = (1,b)

	and a disassembly operation:

		case d of {isA(x) -> E1; isB(x) -> E2}

	This can be generalised to arbitrary numbers of domains.

	See also {smash sum}, {disjoint union}.

	2. <tool> A {Unix} utility to calculate a 16-bit {checksum} of
	the data in a file.  It also displays the size of the file,
	either in {kilobytes} or in 512-byte blocks.  The checksum may
	differ on machines with 16-bit and 32-bit ints.

	{Unix manual page}: sum(1).

	(1995-03-16)

<digital signal processing> The result of measuring the
	amplitude of an analog signal at a specified time.  In
	{digital signal processing} a sample is a signed or unsigned
	number and the number of samples per second is called the
	{sample rate}.

	(2001-06-06)

<architecture> {Data} transferred from a computer system to
	the outside world via some kind of {output device}.

	Opposite: {input}.

	(1997-04-28)

<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)

1. <logic> A {logical formula} in {conjunctive normal form},
	which has the {schema}

	 p1 ^ ...^ pm => q1 V ... V qn.

	or, equivalently,

	 ~p1 V ... V ~pn V q1 V ... V qn,

	where pi and qi are {atoms}.
	
	The operators ~, ^, V, => are {connectives}, where ~ stands
	for {negation}, ^ for {conjunction}, V for {disjunction} and
	=> for {implication}.

	2. <database> A part of a {SQL} statement that does not
	constitute a full statement; for e.g. a "WHERE clause".

	(2004-05-28)