Array (data type)

In <a href="/facts/Computer_science/lN3pEyPz">computer science</a>, array is a <a href="/facts/Data_type/fcx5hgVL">data type</a> that represents a collection of elements (<a href="/facts/Value_(computer_science)/QgQPbewf">values</a> or <a href="/facts/Variable_(computer_science)/VoCKtwml">variables</a>), each selected by one or more indices (identifying keys) that can be computed at <a href="/facts/Run_time_(program_lifecycle_phase)/lCxKsrzB">run time</a> during program execution. Such a collection is usually called an array variable or array value. By analogy with the mathematical concepts <a href="/facts/Vector_(mathematics_and_physics)/U8mM7A5F">vector</a> and <a href="/facts/Matrix_(mathematics)/qa8FI4ko">matrix</a>, array types with one and two indices are often called vector type and matrix type, respectively. More generally, a multidimensional array type can be called a tensor type, by analogy with the mathematical concept, <a href="/facts/Tensor/pNjFo5tV">tensor</a>.
Language support for array types may include certain <a href="/facts/Built-in_type/0c898228">built-in</a> array data types, some syntactic constructions (array type constructors) that the <a href="/facts/Programmer/WGTS1Jv9">programmer</a> may use to define such types and declare array variables, and special notation for indexing array elements. For example, in the <a href="/facts/Pascal_programming_language/b3yvp8bF">Pascal programming language</a>, the declaration type MyTable = array [1..4,1..2] of integer, defines a new array data type called MyTable. The declaration var A: MyTable then defines a variable A of that type, which is an aggregate of eight elements, each being an integer variable identified by two indices. In the Pascal program, those elements are denoted A[1,1], A[1,2], A[2,1], …, A[4,2]. Special array types are often defined by the language's standard <a href="/facts/Library_(computer_science)/xRzL3P7q">libraries</a>.
<a href="/facts/Dynamic_list/Ik4JTgJW">Dynamic lists</a> are also more common and easier to implement[dubious – discuss] than <a href="/facts/Dynamic_array/EtocbTWK">dynamic arrays</a>. Array types are distinguished from <a href="/facts/Record_(computer_science)/1fvSgenB">record</a> types mainly because they allow the element indices to be computed at <a href="/facts/Run_time_(program_lifecycle_phase)/lCxKsrzB">run time</a>, as in the Pascal <a href="/facts/Assignment_statement/kLevAoyJ">assignment</a> A[I,J] := A[N-I,2*J]. Among other things, this feature allows a single iterative <a href="/facts/Statement_(computer_science)/bEkBufqX">statement</a> to process arbitrarily many elements of an array variable.
In more theoretical contexts, especially in <a href="/facts/Type_theory/xj0xzVqI">type theory</a> and in the description of abstract <a href="/facts/Algorithm/fnl5NmRt">algorithms</a>, the terms "array" and "array type" sometimes refer to an <a href="/facts/Abstract_data_type/BaVGSHNP">abstract data type</a> (ADT) also called abstract array or may refer to an <a href="/facts/Associative_array/IFGd2xcP">associative array</a>, a <a href="/facts/Mathematics/pxTouaz4">mathematical</a> model with the basic operations and behavior of a typical array type in most languages – basically, a collection of elements that are selected by indices computed at run-time.
Depending on the language, array types may overlap (or be identified with) other data types that describe aggregates of values, such as <a href="/facts/List_(computing)/9tzhAH6M">lists</a> and <a href="/facts/String_(computer_science)/4ChJu5WS">strings</a>. Array types are often implemented by <a href="/facts/Array_data_structure/BKGvF8AM">array data structures</a>, but sometimes by other means, such as <a href="/facts/Hash_table/Ht4ptDPF">hash tables</a>, <a href="/facts/Linked_list/Ik4JTgJW">linked lists</a>, or <a href="/facts/Search_tree/zJIIMEH8">search trees</a>.

Array (data type) open-in-new

Array (data type)