type

theory, programming (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, structures, unions.

Some languages provide strong typing, others allow implicittype conversion and/or explicit type conversion.

(2002-02-22)