type
(Or "data type") A set of values from
which a variable, constant, function, or other expression may
take its value.
Types supported by most programming languages include
{integers} (usually limited to some range so they will fit in
one {word} of storage), {Booleans}, {real numbers}, and
characters. {Strings} are also common, though they may be
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, {structures}, {unions}.
Some languages provide {strong typing}, others allow {implicit
type conversion} and/or {explicit type conversion}.
(1999-09-19)