<programming> The name given in {Smalltalk} and other
	{object-oriented languages} to a procedure or routine
	associated with one or more {classes}.  An {object} of a
	certain class knows how to perform actions, e.g. printing
	itself or creating a new instance of itself, rather than the
	function (e.g. printing) knowing how to handle different types
	of object.

	Different classes may define methods with the same name
	(i.e. methods may be {polymorphic}).  The term "method" is used
	both for a named operation, e.g. "PRINT" and also for the code
	which a specific class provides to perform tha
	t operation.

	Most methods operate on objects that are instances of a
	certain class.  Some object-oriented languages call these
	"object methods" to distinguish then from "{class methods}".

	In {Smalltalk}, a method is defined by giving its name,
	documentation, temporary local variables and a sequence of
	expressions separated by "."s.

	(2000-03-22)

<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)

<programming> A special value used in several languages to
	represent the thing referred to by an uninitialised pointer.

	<database> A special value that may be stored in some database
	columns to represent an unknown, missing, not applicable, or
	undefined value.  Nulls are treated completely differently
	from ordinary values when evaluating SQL expressions and there
	are several SQL constructs for dealing with nulls.

	(2003-06-17)

<programming> (Or "parameter") A name in a {function} or
	{subroutine} definition that is replaced by, or bound to, the
	corresponding {actual argument} when the function or
	subroutine is called.  In many languages formal arguments
	behave like {local variables} which get initialised on entry.

	See: {argument}.

	(2002-07-02)

<programming> (ORB) Part of the {OMG} {CORBA} specification,
	an ORB's basic function is to pass {method} invocation
	requests to the correct {objects} and return the results to
	the caller.

	To achieve this the ORB must be able must be able to identify
	and locate objects, handle connections from invoker and the
	data returned from methods.  Communication between the ORB and
	applications are achieved through {IDL} stubs and skeletons
	whilst the OMG has specified {IIOP} as the protocol through
	which ORBs may communicate with each other.  Using IIOP, an
	ORB may request method invocations from a remote object.

	(2003-11-21)

<standard, programming> (CORBA) An {Object Management Group}
	specification which provides a standard messaging interface
	between distributed {objects}.

	The original CORBA specification (1.1) has been revised
	through version 2 (CORBA 2) with the latest specification
	being version 3 (CORBA 3).  In its most basic form CORBA
	consists of the {Interface Definition Language} (IDL) and the
	Dynamic Invocation Interface (DII).

	The IDL definition is complied into a Stub (client) and
	Skeleton (server) component that communicate through an
	{Object Request Broker} (ORB).  When an ORB determines that a
	request is to a remote object, it may execute the request by
	communicating with the remote ORB.

	The Corba IDL can be mapped to a number of languages including
	{C}, {C++}, {Java}, {COBOL}, {Smalltalk}, {Ada}, {Lisp},
	{Python}, and {IDLscript}.  CORBA ORBs are widely available
	for a number of platforms.  The OMG standard for inter-ORB
	communication is {IIOP}, this ensures that all CORBA 2
	compliant ORBS are able to interoperate.

	See also {COSS}, {Component Object Model}, {RMI}.

	{OMG CORBA site (http://www.corba.org/)}.

	(2003-11-21)

<programming, operating system> A {variable} that is bound in
	the current environment.  When evaluating an expression in
	some environment, the evaluation of a variable consists of
	looking up its name in the environment and substituting its
	value.

	Most programming languages have some concept of an environment
	but in {Unix} {shell scripts} it has a specific meaning
	slightly different from other contexts.  In shell scripts,
	environment variables are one kind of {shell variable}.  They
	differ from {local variables} and {command line arguments} in
	that they are inheritted by a {child process}.  Examples are
	the PATH variable that tells the shell the {file system}
	{paths} to search to find command {executables} and the TZ
	variable which contains the local time zone.  The variable
	called "SHELL" specifies the type of shell being used.

	These variables are used by commands or {shell scripts} to
	discover things about the environment they are operating in.
	Environment variables can be changed or created by the {user}
	or a program.

	To see a list of environment variables type "setenv" at the
	{csh} or {tcsh} {prompt} or "set" at the {sh}, {bash}, {jsh}
	or {ksh} prompt.

	In other programming languages, e.g. {functional programming}
	languages, the environment is extended with new bindings when
	a {function}'s {parameters} are bound to its {actual
	arguments} or when new variables are declared.  In a
	{block-structured} {procedural} language, the environment
	usually consists of a {linked list} of {activation records}.

	(1999-01-26)

<programming> (Or "unfold") To replace a {function} call with
	an instance of the function's body.  {Actual argument}
	expressions are substituted for {formal parameters} as in
	{beta reduction}.  Inlining is usually done as a
	{compile-time} transformation.

	If done recklessly (e.g. attempting to inline a {recursive}
	function) the {compiler} will fail to terminate.  If done
	over-enthusiastically the code size may increase
	exponentially, e.g. if function f calls g twice, and g calls h
	twice and h is inlined in g which is inlined in f (in either
	order) then there will be four copies of h's body in f.

	See also {linear argument}, {unfold/fold}.

	(1994-11-03)

<language>

	1. {Interactive Data analysis Language} ({Xerox}).

	2. {Interface Description Language} (Snodgrass, UNC, Arizona).

	3. {Interface Definition Language} ({SunSoft}, {OMG}).

	4. {Interactive Data Language} ({Research Systems}).

	(2004-05-07)

<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)

<language> (Or "Operator overloading").  Use of a single
	symbol to represent operators with different argument types,
	e.g. "-", used either, as a {monadic} operator to negate an
	expression, or as a {dyadic} operator to return the difference
	between two expressions.  Another example is "+" used to add
	either integers or {floating-point} numbers.  Overloading is
	also known as ad-hoc {polymorphism}.

	User-defined operator overloading is provided by several
	modern programming languages, e.g. {C++}'s {class} system and
	the {functional programming} language {Haskell}'s {type
	class}es.

	(1995-04-30)

1. <mathematics> (Or "map", "mapping") If D and C are sets
	(the domain and codomain) then a function f from D to C,
	normally written "f : D -> C" is a subset of D x C such that:

	1. For each d in D there exists some c in C such that (d,c) is
	an element of f.  I.e. the function is defined for every
	element of D.

	2. For each d in D, c1 and c2 in C, if both (d,c1) and (d,c2)
	are elements of f then c1 = c2.  I.e. the function is uniquely
	defined for every element of D.

	See also {image}, {inverse}, {partial function}.

	2. <programming> Computing usage derives from the mathematical
	term but is much less strict.  In programming (except in
	{functional programming}), a function may return different
	values each time it is called with the same argument values
	and may have {side effects}.

	A {procedure} is a function which returns no value but has
	only {side-effects}.  The {C} language, for example, has no
	procedures, only functions.  {ANSI C} even defines a {type},
	{void}, for the result of a function that has no result.

	(1996-09-01)

1. <language, programming> {programming language}.

	2. <human language> {natural language}.

	(1998-09-07)

<programming> (RMI) Part of the {Java} {programming language}
	{library} which enables a Java program running on one computer
	to access the {objects} and {methods} of another Java program
	running on a different computer.

	{Home
	(http://java.sun.com/products/jdk/1.1/docs/guide/rmi/index.html)}.

	(1997-09-04)

<library, networking> {Berkeley} {Unix} networking {socket}
	library routine to satisfy a connection request from a remote
	{host}.  A specified socket on the local host (which must be
	capable of accepting the connection) is connected to the
	requesting socket on the remote host.  The remote socket's
	socket address is returned.

	{Unix manual pages}: accept(2), connect(2).

	(1994-11-08)