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)

<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)

{Software Developers Kit} (or "Software Development Kit").

<operating system, programming> The process of carrying out
	the {instructions} in a computer program by a computer.

	See also {dry run}.

	(1996-05-13)

1. A discrepancy between a computed, observed, or measured
	value or condition and the true, specified, or theoretically
	correct value or condition.

	2. <programming> A mental mistake made by a programmer that
	may result in a program {fault}.

	3. (verb) What a program does when it stops as result of a
	programming error.

	(2000-03-28)

In {object-oriented programming} sending a message to an
	{object} (to invoke a {method}) is equivalent to calling a
	{procedure} in traditional programming languages, except that
	the actual code executed may only be selected at run time
	depending on the {class} of the object.  Thus, in response to
	the message "drawSelf", the method code invoked would be
	different if the target object were a circle or a square.

	(1995-02-16)

1. See {multithreading}.

	2. See {threaded code}.

	3. {topic thread}.

	[{Jargon File}]

1. The {supervisor} program or {operating system} on a
	computer.

	2. The entire computer system, including input/output devices,
	the {supervisor} program or {operating system} and possibly
	other {software}.

	3. Any large program.

	4. Any method or {algorithm}.

	[{Jargon File}]

<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)