<software> Instructions for a computer in some programming
	language, often {machine language}.  The word "code" is often
	used to distinguish instructions from {data} (e.g. "The code
	is marked 'read-only'") whereas "{software}" is used in
	contrast with "{hardware}" and may consist of more than just
	code.

	(2000-04-08)

1. <mathematics> A collection of {nodes} and {edges}.

	See also {connected graph}, {degree}, {directed graph}, {Moore
	bound}, {regular graph}, {tree}.

	2. <graphics> A visual representation of algebraic equations
	or data.

	(1996-09-22)

1. <programming> The prototype for an {object} in an
	{object-oriented language}; analogous to a {derived type} in a
	{procedural language}.  A class may also be considered to be a
	set of objects which share a common structure and behaviour.
	The structure of a class is determined by the {class
	variables} which represent the {state} of an object of that
	class and the behaviour is given by a set of {methods}
	associated with the class.

	Classes are related in a {class hierarchy}.  One class may be
	a specialisation (a "{subclass}") of another (one of its
	"{superclasses}") or it may be composed of other classes or it
	may use other classes in a {client-server} relationship.  A
	class may be an {abstract class} or a {concrete class}.

	See also {signature}.

	2. <programming> See {type class}.

	3. <networking> One of three types of {Internet addresses}
	distinguished by their most significant bits.

	3. <language> A language developed by the {Andrew Project}.
	It was one of the first attempts to add {object-oriented}
	features to {C}.

	(1995-05-01)

<programming> (Or "arg") A value or reference passed to a
	{function}, {procedure}, {subroutine}, command or program, by
	the caller.  For example, in the function definition

		square(x) = x * x

	x is the {formal argument} or "parameter", and in the call

		y = square(3+4)

	3+4 is the {actual argument}.  This will execute the function
	square with x having the value 7 and return the result 49.

	There are many different conventions for passing arguments to
	functions and procedures including {call-by-value},
	{call-by-name}, {call-by-reference}, {call-by-need}.  These
	affect whether the value of the argument is computed by the
	caller or the callee (the function) and whether the callee can
	modify the value of the argument as seen by the caller (if it
	is a variable).

	Arguments to functions are usually, following mathematical
	notation, written in parentheses after the function name,
	separated by commas (but see {curried function}).  Arguments
	to a program are usually given after the command name,
	separated by spaces, e.g.:

		cat myfile yourfile hisfile

	Here "cat" is the command and "myfile", "yourfile", and
	"hisfile" are the arguments.

	(2006-05-27)

<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, tool> A program that converts another program
	from some {source language} (or {programming language}) to
	{machine language} (object code).  Some compilers output
	{assembly language} which is then converted to {machine
	language} by a separate {assembler}.

	A compiler is distinguished from an assembler by the fact that
	each input statement does not, in general, correspond to a
	single machine instruction or fixed sequence of instructions.
	A compiler may support such features as automatic allocation
	of variables, arbitrary arithmetic expressions, control
	structures such as FOR and WHILE loops, variable {scope},
	input/ouput operations, {higher-order functions} and
	{portability} of source code.

	{AUTOCODER}, written in 1952, was possibly the first primitive
	compiler.  {Laning and Zierler}'s compiler, written in
	1953-1954, was possibly the first true working algebraic
	compiler.

	See also {byte-code compiler}, {native compiler}, {optimising
	compiler}.

	(1994-11-07)

Loosely used to mean "in accordance with all the relevant
	rules", especially in connection with some set of constraints
	defined by software.  "The older =+ alternate for += is no
	longer legal syntax in ANSI C."  "This parser processes each
	line of legal input the moment it sees the trailing linefeed."
	Hackers often model their work as a sort of game played with
	the environment in which the objective is to maneuver through
	the thicket of "natural laws" to achieve a desired objective.
	Their use of "legal" is flavoured as much by this game-playing
	sense as by the more conventional one having to do with courts
	and lawyers.  Compare {language lawyer}, {legalese}.

	[{Jargon File}]

1. <mathematics> {Base} two.  A number representation
	consisting of zeros and ones used by practically all computers
	because of its ease of implementation using digital
	electronics and {Boolean algebra}.

	2. <file format> {binary file}.

	3. <programming> A description of an {operator} which takes
	two {arguments}.  See also {unary}, {ternary}.

	(2005-02-21)

<jargon> Different systems (e.g., {programs}, {file formats},
	{protocols}, even {programming languages}) that can work
	together or exchange data are said to be compatible.

	See also {backward compatible}, {forward compatible}.

	(1998-01-15)

<theory, programming> (Or "data type") A set of values from
	which a {variable}, {constant}, {function}, or other
	{expression} may take its value.  A type is a classification
	of data that tells the {compiler} or {interpreter} how the
	programmer intends to use it.  For example, the process and
	result of adding two variables differs greatly according to
	whether they are integers, floating point numbers, or strings.

	Types supported by most programming languages include
	{integers} (usually limited to some range so they will fit in
	one {word} of storage), {Booleans}, {floating point numbers},
	and characters.  {Strings} are also common, and are
	represented as {lists} of characters in some languages.

	If s and t are types, then so is s -> t, the type of
	{functions} from s to t; that is, give them a term of type s,
	functions of type s -> t will return a term of type t.

	Some types are {primitive} - built-in to the language, with no
	visible internal structure - e.g. Boolean; others are
	composite - constructed from one or more other types (of
	either kind) - e.g. {lists}, {arrays}, {structures}, {unions}.
	{Object-oriented programming} extends this with {classes}
	which encapsulate both the structure of a type and the
	operations that can be performed on it.

	Some languages provide {strong typing}, others allow {implicit
	type conversion} and/or {explicit type conversion}.

	(2003-12-22)

<programming> Any piece of program code in a {high-level
	language} which, when (if) its execution terminates, returns a
	value.  In most programming languages, expressions consist of
	constants, variables, operators, functions, and {parentheses}.
	The operators and functions may be built-in or user defined.
	Languages differ on how expressions of different {types} may
	be combined - with some combination of explicit {casts} and
	implicit {coercions}.

	The {syntax} of expressions generally follows conventional
	mathematical notation, though some languages such as {Lisp} or
	{Forth} have their own idiosyncratic syntax.

	(2001-05-14)

<hardware> A {SCSI} device that executes a command from a
	{SCSI initiator} to perform some task.  Typically the target
	is a SCSI peripheral device but the {host adapter} can also be
	a target.

	(1999-02-10)

<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)

1. (Obsolete) The source code for a program, which may be in
	any language, as opposed to the linkable or executable binary
	produced from it by a compiler.  The idea behind the term is
	that to a real hacker, a program written in his favourite
	programming language is at least as readable as English.
	Usage: mostly by old-time hackers, though recognisable in
	context.

	2. The official name of the {database} language used by the
	{Pick} {operating system}, actually a sort of {crufty},
	brain-damaged {SQL} with delusions of grandeur.  The name
	permits {marketroids} to say "Yes, and you can program our
	computers in English!" to ignorant {suits} without quite
	running afoul of the truth-in-advertising laws.

	["Exploring the Pick Operating System", J.E. Sisk et al,
	Hayden 1986].

	[{Jargon File}]