Data (computer science): Difference between revisions

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{{other uses|Data (disambiguation)|Datum (disambiguation)}}

{{broader|Data}}

{{Merge to|Digital data|discuss=Talk:Digital data#Proposed merge of Data (computer science) into Digital data|date=March 2025}}

[[File:Data types - en.svg|thumb|Various types of data which can be visualized through a computer device.]]

In [[computer science]], '''data''' (treated as singular, plural, or as a [[mass noun]]) is [[Data|any sequence of one or more [[symbolsymbols]]s; '''datum''' is a single symbolunit of data. Data requires [[Interpretation (logic)|interpretation]] to become [[information]]. ''[[Digital data]]'' is data that is represented using the [[binary number]] system of ones (1) and zeros (0), instead of [[analogAnalog signature signalanalysis|analog]] representation. In modern (post-1960) computer systems, all data is digital.

Data exists in three states: [[data at rest]], [[data in transit]] and [[data in use]]. Data within a computer, in most cases, [[Parallel communication|moves as parallel data]]. Data moving to or from a computer, in most cases, [[Serial communication|moves as serial data]]. Data sourced from an analog device, such as a temperature sensor, may be converted to digital using an [[analog-to-digital converter]]. Data representing [[Quantity|quantities]], characters, or symbols on which operations are performed by a [[computer]] are [[Data storage|stored]] and [[Record (computer science)|recorded]] on [[magnetic tape data storage|magnetic]], [[optical storage|optical]], electronic, or mechanical recording media, and [[Data communication|transmitted]] in the form of digital electrical or optical signals.<ref>{{cite web|url=https://www.lexico.com/en/definition/data|title=Data|work=Lexico|access-date=14 January 2022|url-status=dead|archive-url=https://web.archive.org/web/20190623094330/https://www.lexico.com/en/definition/data |archive-date=2019-06-23 }}</ref> Data pass in and out of computers via [[peripheral|peripheral devices]].

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To store data [[byte]]s in a file, they have to be [[Serialization|serialized]] in a [[file format]]. Typically, programs are stored in special file types, different from those used for other data. [[Executable|Executable file]]s contain programs; all other files are also [[data file]]s. However, executable files may also contain data used by the program which is built into the program. In particular, some executable files have a [[data segment]], which nominally contains constants and initial values for variables, both of which can be considered data.

The line between program and data can become blurry. An [[interpreter (computing)|interpreter]], for example, is a program. The input data to an interpreter is itself a program, just not one expressed in native [[Machine code|machine language]]. In many cases, the interpreted program will be a human-readable [[text file]], which is manipulated with a [[text editor]] program. [[Metaprogramming]] similarly involves programs manipulating other programs as data. Programs like [[compiler]]s, [[Linker (computing)|linker]]s, [[debugger]]s, [[Software Updater|program updaters]], [[Antivirus software|virus scanners]] and such use other programs as their data.

For example, a [[user (computing)|user]] might first instruct the [[operating system]] to load a [[word processor]] program from one file, and then use the running program to open and edit a [[Document file format|document]] stored in another file. In this example, the document would be considered data. If the word processor also features a [[spell checker]], then the dictionary (word list) for the spell checker would also be considered data. The [[algorithm]]s used by the spell checker to suggest corrections would be either [[machine code]] data or text in some interpretable [[programming language]].

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===Abstraction and indirection===

* [[Object-oriented programming]] uses two basic concepts for understanding data and software:

# The taxonomic rank-structure of ''[[Class (computer programming)|classes]]'', which is an example run time, the creation of referencesa tohierarchical in-zg)#Objectdata lisstructure; liband

# at run time, the creation of references to in-memory data-structures of objects that have been [[Instance (computer science)|instantiated]] from a [[Library (computing)#Object libraries|class library]].

It is only after instantiation that an objenobject of a specified class exists. After an object's ryreference is cleared, the object also ceases to exist. The memory locations where the object's data was stornstored are [[Garbage collection (computer science)|garbage]] and are reclassified as unused memory available for reuse.

===Database data===

* The advent of [[database]]s introduced a further [[Abstraction layer|layer of abstraction]] for persisteentpersistent data storage. Databases use [[metadata]], and a [[SQL|structured query language]] protocol between [[Client–server model|client and server]] systems, ccatingcommunicating over a [[compcomputer network]], using a [[Two-phase commit protocol|two phase commit]] logging system to ensure [[Database transaction|transactional]] completeness, when saving data.

===Parallel distributed data processing===

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==See also==

{{div col|colmcolwidth=20em}}

* [[BiBig data]]

* [[Data]]

* [[Data dictionary]]

* [[Data modeling]]

* [[Data stream]]

* [[Data set]]

* [[Database index]]

* [[State (computer science)]]

* [[Tuple]]

{{div col end}}

==References==

{{reflist}}

{{data}}

{{Authority contcontrol}}

[[Category:Computer data| ]]