Data structure

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For other uses, see Data structure (disambiguation). Data structure_sentence_0

Not to be confused with data type. Data structure_sentence_1

In computer science, a data structure is a data organization, management, and storage format that enables efficient access and modification. Data structure_sentence_2

More precisely, a data structure is a collection of data values, the relationships among them, and the functions or operations that can be applied to the data. Data structure_sentence_3

Usage Data structure_section_0

Data structures serve as the basis for abstract data types (ADT). Data structure_sentence_4

The ADT defines the logical form of the data type. Data structure_sentence_5

The data structure implements the physical form of the data type. Data structure_sentence_6

Different types of data structures are suited to different kinds of applications, and some are highly specialized to specific tasks. Data structure_sentence_7

For example, relational databases commonly use B-tree indexes for data retrieval, while compiler implementations usually use hash tables to look up identifiers. Data structure_sentence_8

Data structures provide a means to manage large amounts of data efficiently for uses such as large databases and internet indexing services. Data structure_sentence_9

Usually, efficient data structures are key to designing efficient algorithms. Data structure_sentence_10

Some formal design methods and programming languages emphasize data structures, rather than algorithms, as the key organizing factor in software design. Data structure_sentence_11

Data structures can be used to organize the storage and retrieval of information stored in both main memory and secondary memory. Data structure_sentence_12

Implementation Data structure_section_1

Data structures are generally based on the ability of a computer to fetch and store data at any place in its memory, specified by a pointer—a bit string, representing a memory address, that can be itself stored in memory and manipulated by the program. Data structure_sentence_13

Thus, the array and record data structures are based on computing the addresses of data items with arithmetic operations, while the linked data structures are based on storing addresses of data items within the structure itself. Data structure_sentence_14

The implementation of a data structure usually requires writing a set of procedures that create and manipulate instances of that structure. Data structure_sentence_15

The efficiency of a data structure cannot be analyzed separately from those operations. Data structure_sentence_16

This observation motivates the theoretical concept of an abstract data type, a data structure that is defined indirectly by the operations that may be performed on it, and the mathematical properties of those operations (including their space and time cost). Data structure_sentence_17

Examples Data structure_section_2

Main article: List of data structures Data structure_sentence_18

There are numerous types of data structures, generally built upon simpler primitive data types: Data structure_sentence_19

Data structure_unordered_list_0

  • An array is a number of elements in a specific order, typically all of the same type (depending on the language, individual elements may either all be forced to be the same type, or may be of almost any type). Elements are accessed using an integer index to specify which element is required. Typical implementations allocate contiguous memory words for the elements of arrays (but this is not always a necessity). Arrays may be fixed-length or resizable.Data structure_item_0_0
  • A linked list (also just called list) is a linear collection of data elements of any type, called nodes, where each node has itself a value, and points to the next node in the linked list. The principal advantage of a linked list over an array is that values can always be efficiently inserted and removed without relocating the rest of the list. Certain other operations, such as random access to a certain element, are however slower on lists than on arrays.Data structure_item_0_1
  • A record (also called tuple or struct) is an aggregate data structure. A record is a value that contains other values, typically in fixed number and sequence and typically indexed by names. The elements of records are usually called fields or members.Data structure_item_0_2
  • A union is a data structure that specifies which of a number of permitted primitive types may be stored in its instances, e.g. float or long integer. Contrast with a record, which could be defined to contain a float and an integer; whereas in a union, there is only one value at a time. Enough space is allocated to contain the widest member datatype.Data structure_item_0_3
  • A tagged union (also called variant, variant record, discriminated union, or disjoint union) contains an additional field indicating its current type, for enhanced type safety.Data structure_item_0_4
  • An object is a data structure that contains data fields, like a record does, as well as various methods which operate on the data contents. An object is an in-memory instance of a class from a taxonomy. In the context of object-oriented programming, records are known as plain old data structures to distinguish them from objects.Data structure_item_0_5

In addition, graphs and binary trees are other commonly used data structures. Data structure_sentence_20

Language support Data structure_section_3

Most assembly languages and some low-level languages, such as BCPL (Basic Combined Programming Language), lack built-in support for data structures. Data structure_sentence_21

On the other hand, many high-level programming languages and some higher-level assembly languages, such as MASM, have special syntax or other built-in support for certain data structures, such as records and arrays. Data structure_sentence_22

For example, the C (a direct descendant of BCPL) and Pascal languages support structs and records, respectively, in addition to vectors (one-dimensional arrays) and multi-dimensional arrays. Data structure_sentence_23

Most programming languages feature some sort of library mechanism that allows data structure implementations to be reused by different programs. Data structure_sentence_24

Modern languages usually come with standard libraries that implement the most common data structures. Data structure_sentence_25

Examples are the C++ Standard Template Library, the Java Collections Framework, and the Microsoft .NET Framework. Data structure_sentence_26

Modern languages also generally support modular programming, the separation between the interface of a library module and its implementation. Data structure_sentence_27

Some provide opaque data types that allow clients to hide implementation details. Data structure_sentence_28

Object-oriented programming languages, such as C++, Java, and Smalltalk, typically use classes for this purpose. Data structure_sentence_29

Many known data structures have concurrent versions which allow multiple computing threads to access a single concrete instance of a data structure simultaneously. Data structure_sentence_30

See also Data structure_section_4

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: structure.