<programming> One of a sequence of copies of a program, each
	incorporating new modifications.  Each version is usually
	identified by a number, commonly of the form X.Y where X is
	the major version number and Y is the release number.
	Typically an increment in X (with Y reset to zero) signifies a
	substantial increase in the function of the program or a
	partial or total re-implementation, whereas Y increases each
	time the progam is changed in any way and re-released.

	Version numbers are useful so that the user can know if the
	program has changed ({bugs} have been fixed or new functions
	added) since he obtained his copy and the programmer can tell
	if a bug report relates to the current version.  It is thus
	always important to state the version when reporting bugs.
	Statements about compatibility between different software
	components should always say which versions they apply to.

	See {change management}.

	(1997-12-07)

<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)

<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)