<convention, data> A string unique to a time duration of 24
	hours between 2 successive midnights defined by the local time
	zone.  The specific representation of a date will depend on
	which calendar convention is in force; e.g., Gregorian,
	Islamic, Japanese, Chinese, Hebrew etc. as well as local
	ordering conventions such as UK: day/month/year, US:
	month/day/year.

	Inputting and outputting dates on computers is greatly
	complicated by these {localisation} issues which is why they
	tend to operate on dates internally in some unified form such
	as seconds past midnight at the start of the first of January
	1970.

	Many software and hardware representations of dates allow only
	two digits for the year, leading to the {year 2000} problem.

	{Unix manual page}: date(1), ctime(3).

	(1997-07-11)

<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. <file system> {hard link} or {symbolic link}.

	2. <hypertext> {hyperlink}.

	(1997-10-22)

1. Executable code, especially a "pure code" portion shared
	between multiple instances of a program running in a
	{multitasking} {operating system}.

	Compare {English}.

	2. Textual material in the mainstream sense; data in ordinary
	{ASCII} or {EBCDIC} representation (see {flat ASCII}).  "Those
	are text files; you can review them using the editor."

	These two contradictory senses confuse hackers too.

	[{Jargon File}]

	(1995-03-16)

<data, database> An area of a {database} {record}, or
	{graphical user interface} {form}, into which a particular
	item of data is entered.

	Example usage: "The telephone number field is not really a
	numerical field", "Why do we need a four-digit field for the
	year?".

	A {database} {column} is the set of all instances of a given
	field from all records in a {table}.

	(1999-04-26)

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)

<programming> (Sometimes "var" /veir/ or /var/) A named memory
	location in which a program can store intermediate results and
	from which it can read it them.  Each {programming language}
	has different rules about how variables can be named, typed,
	and used.  Typically, a value is "assigned" to a variable in
	an {assignment} statement.  The value is obtained by
	evaluating an expression and then stored in the variable.  For
	example, the assignment

		x = y + 1

	means "add one to y and store the result in x".  This may look
	like a mathematical equation but the mathematical equality is
	only true in the program until the value of x or y changes.
	Furthermore, statements like

		x = x + 1

	are common.  This means "add one to x", which only makes sense
	as a state changing operation, not as a mathematical equality.

	The simplest form of variable corresponds to a single-{word}
	of {memory} or a {CPU} {register} and an assignment to a
	{load} or {store} {machine code} operation.

	A variable is usually defined to have a {type}, which never
	changes, and which defines the set of values the variable can
	hold.  A type may specify a single ("atomic") value or a
	collection ("aggregate") of values of the same or different
	types.  A common aggregate type is the {array} - a set of
	values, one of which can be selected by supplying a numerical
	{index}.

	Languages may be {untyped}, {weakly typed}, {strongly typed},
	or some combination.  {Object-oriented programming} languages
	extend this to {object} types or {classes}.

	A variable's {scope} is the region of the program source
	within which it represents a certain thing.  Scoping rules are
	also highly language dependent but most serious languages
	support both {local variables} and {global variables}.
	{Subroutine} and {function} {formal arguments} are special
	variables which are set automatically by the language runtime
	on entry to the subroutine.

	In a {functional programming} language, a variable's value
	never changes and change of state is handled as recursion over
	lists of values.

	(2004-11-16)

<object-oriented> In {object-oriented programming}, an
	instance of the data structure and behaviour defined by the
	object's {class}.  Each object has its own values for the
	{instance variables} of its class and can respond to the
	{methods} defined by its class.

	For example, an object of the "Point" class might have
	instance variables "x" and "y" and might respond to the "plot"
	method by drawing a dot on the screen at those coordinates.

	(2004-01-26)

<programming> A constant made available to a process, by
	inclusion in the executable text.  Most modern systems do not
	allow texts to modify themselves during execution, so literals
	are indeed constant; their value is written at compile-time
	and is read-only at run time.

	In contrast, values placed in variables or files and accessed
	by the process via a symbolic name, can be changed during
	execution.  This may be an asset.  For example, messages can
	be given in a choice of languages by placing the translation
	in a file.

	Literals are used when such modification is not desired.  The
	name of the file mentioned above (not its content), or a
	physical constant such as 3.14159, might be coded as a
	literal.  Literals can be accessed quickly, a potential
	advantage of their use.

	(1996-01-23)

1. <software> An occurrence or happening of significance to a
	task or program, such as the completion of an asynchronous
	input/output operation.  A task may wait for an event or any
	of a set of events or it may (request to) receive asynchronous
	notification (a {signal} or {interrupt}) that the event has
	occurred.

	See also {event-driven}.

	2. <data> A transaction or other activity that affects the
	records in a file.

	(2000-02-09)

<hypertext, World-Wide Web, standard> (HTML) A {hypertext}
	document format used on the {World-Wide Web}.  HTML is built
	on top of {SGML}.  "Tags" are embedded in the text.  A tag
	consists of a "<", a "directive" (in lower case), zero or
	more parameters and a ">".  Matched pairs of directives, like
	"<title>" and "</title>" are used to delimit text which is to
	appear in a special place or style.

	Links to other documents are in the form

	 <a href="http://machine.edu/subdir/file.html">foo</a>

	where "<a>" and "</a>" delimit an "anchor", "href" introduces
	a hypertext reference, which is most often a {Uniform Resource
	Locator} (URL) (the string in double quotes in the example
	above).  The link will be represented in the browser by the
	text "foo" (typically shown underlined and in a different
	colour).

	A certain place within an HTML document can be marked with a
	named anchor, e.g.:

	 <a name="baz">

	The "fragment identifier", "baz", can be used in an href by
	appending "#baz" to the document name.

	Other common tags include <p> for a new paragraph, <b>..</b>
	for bold text, <ul> for an unnumbered list, <pre> for
	preformated text, <h1>, <h2> .. <h6> for headings.

	{HTML} supports some standard {SGML} {national characters} and
	other non-{ASCII} characters through special {escape
	sequences}, e.g. "&eacute;" for a lower case 'e' with an acute
	accent.  You can sometimes get away without the terminating
	semicolon but it's bad style.

	Most systems will ignore the case of tags and attributes but
	lower case should be used for compatibility with {XHTML}.

	The {World-Wide Web Consortium} (W3C) is the international
	{standards} body for HTML.

	Latest version: {XHTML} 1.0, as of 2000-09-10.

	{Home (http://www.w3.org/MarkUp/)}.

	{Character escape sequences
	(http://www.w3.org/hypertext/WWW/MarkUp/ISOlat1.html)}.

	See also {weblint}.

	(2006-01-19)

<hypertext, standard, World-Wide Web> (XHTML) A reformulation
	of {HTML} 4.01 in {XML}.  Being XML means that XHTML can be
	viewed, edited, and validated with standard XML tools.  At the
	same time, it operates as well as or better than HTML 4 in
	existing HTML 4 conforming user agents.

	The most important change is that all elements must be
	terminated, either with a closing tag or using the <tag.../>
	shorthand.  So, instead of

		<input type=submit>

	you would write

		<input type="submit" />

	The space before the "/" is required by some older browsers.
	Other differences are that tag and attribute names should be
	lower case and all attributes should be quoted.

	{XHTML Home (http://www.w3.org/TR/xhtml1/)}.

	{Quick Summary
	(http://www.technorealm.co.uk/design/html-to-xhtml-conversions.html)}

	Latest version: 1.0 Second Edition 2002-08-01, as of 2004-03-16.

	(2006-01-19)

1. <application, algorithm> To arrange a collection of items
	in some specified order.  The items - {records} in a file or
	data structures in memory - consist of one or more {fields} or
	members.  One of these fields is designated as the "sort key"
	which means the records will be ordered according to the value
	of that field.  Sometimes a sequence of key fields is
	specified such that if all earlier keys are equal then the
	later keys will be compared.  Within each field some ordering
	is imposed, e.g. ascending or descending numerical, {lexical
	ordering}, or date.

	Sorting is the subject of a great deal of study since it is a
	common operation which can consume a lot of computer time.
	There are many well-known sorting {algorithms} with different
	time and space behaviour and programming {complexity}.

	Examples are {quicksort}, {insertion sort}, {bubble sort},
	{heap sort}, and {tree sort}.  These employ many different
	data structures to store sorted data, such as {arrays},
	{linked lists}, and {binary trees}.

	2. <tool> The {Unix} utility program for sorting lines of
	files.

	{Unix manual page}: sort(1).

	(1997-02-12)

1. Non-functional; {down}; {crash}ed.  Especially used of
	{hardware}.

	2. At {XEROX PARC}, software that is working but not
	undergoing continued development and support.

	[{Jargon File}]

1. <chat> {Unix}'s simple {talk} command and {protocol}.
	write has been largely superseded by {talk} and then {irc}.

	An enhancement, {RWP}, has been proposed.

	2. <tool> A simple {text editor} for {Windows}.

	(1998-04-28)