type
data type

    (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)