1. <programming> A collection of identically typed data items
	distinguished by their indices (or "subscripts").  The number
	of dimensions an array can have depends on the language but is
	usually unlimited.

	An array is a kind of {aggregate} data type.  A single
	ordinary variable (a "{scalar}") could be considered as a
	zero-dimensional array.  A one-dimensional array is also known
	as a "{vector}".

	A reference to an array element is written something like
	A[i,j,k] where A is the array name and i, j and k are the
	indices.  The {C} language is peculiar in that each index is
	written in separate brackets, e.g. A[i][j][k].  This expresses
	the fact that, in C, an N-dimensional array is actually a
	vector, each of whose elements is an N-1 dimensional array.

	Elements of an array are usually stored contiguously.
	Languages differ as to whether the leftmost or rightmost index
	varies most rapidly, i.e. whether each row is stored
	contiguously or each column (for a 2D array).

	Arrays are appropriate for storing data which must be accessed
	in an unpredictable order, in contrast to {lists} which are
	best when accessed sequentially.

	See also {associative array}.

	2. <architecture> A {processor array}, not to be confused with
	an {array processor}.

	(1995-01-25)

[{Usenet}] 1. To duplicate a portion (or whole) of another's
	message (typically with attribution to the source) in a reply
	or followup, for clarifying the context of one's response.
	See the discussion of inclusion styles under "Hacker Writing
	Style".

	2. [{C}] "#include <disclaimer.h>" has appeared in {sig
	blocks} to refer to a notional "standard {disclaimer} file".

	[{Jargon File}]

1. <philosophy, mathematics> A branch of philosophy and
	mathematics that deals with the formal principles, methods and
	criteria of validity of {inference}, reasoning and
	{knowledge}.

	Logic is concerned with what is true and how we can know
	whether something is true.  This involves the formalisation of
	logical arguments and {proofs} in terms of symbols
	representing {propositions} and {logical connectives}.  The
	meanings of these logical connectives are expressed by a set
	of rules which are assumed to be self-evident.

	{Boolean algebra} deals with the basic operations of truth
	values: AND, OR, NOT and combinations thereof.  {Predicate
	logic} extends this with existential and universal
	{quantifiers} and symbols standing for {predicates} which may
	depend on variables.  The rules of {natural deduction}
	describe how we may proceed from valid premises to valid
	conclusions, where the premises and conclusions are
	expressions in {predicate logic}.

	Symbolic logic uses a {meta-language} concerned with truth,
	which may or may not have a corresponding expression in the
	world of objects called existance.  In symbolic logic,
	arguments and {proofs} are made in terms of symbols
	representing {propositions} and {logical connectives}.  The
	meanings of these begin with a set of rules or {primitives}
	which are assumed to be self-evident.  Fortunately, even from
	vague primitives, functions can be defined with precise
	meaning.

	{Boolean logic} deals with the basic operations of {truth
	values}: AND, OR, NOT and combinations thereof.  {Predicate
	logic} extends this with {existential quantifiers} and
	{universal quantifiers} which introduce {bound variables}
	ranging over {finite} sets; the {predicate} itself takes on
	only the values true and false.  Deduction describes how we
	may proceed from valid {premises} to valid conclusions, where
	these are expressions in {predicate logic}.

	Carnap used the phrase "rational reconstruction" to describe
	the logical analysis of thought.  Thus logic is less concerned
	with how thought does proceed, which is considered the realm
	of psychology, and more with how it should proceed to discover
	truth.  It is the touchstone of the results of thinking, but
	neither its regulator nor a motive for its practice.

	See also fuzzy logic, logic programming, arithmetic and logic unit,
	first-order logic,

	See also {Boolean logic}, {fuzzy logic}, {logic programming},
	{first-order logic}, {logic bomb}, {combinatory logic},
	{higher-order logic}, {intuitionistic logic}, {equational
	logic}, {modal logic}, {linear logic}, {paradox}.

	2. <electronics> {Boolean} logic circuits.

	See also {arithmetic and logic unit}, {asynchronous logic},
	{TTL}.

	(1995-03-17)

1. <mathematics> A single number, as opposed to a {vector} or
	{matrix} of numbers.  Thus, for example, "scalar
	multiplication" refers to the operation of multiplying one
	number (one scalar) by another and is used to contrast this
	with "matrix multiplication" etc.

	2. <architecture> In a {parallel processor} or {vector
	processor}, the "scalar processor" handles all the sequential
	operations - those which cannot be parallelised or vectorised.

	See also {superscalar}.

	3. <programming> Any data type that stores a single value
	(e.g. a number or {Boolean}), as opposed to an {aggregate}
	data type that has many elements.  A {string} is regarded as a
	scalar in some languages (e.g. {Perl}) and a vector of
	{characters} in others (e.g. {C}).

	(2002-06-12)