Computer file: Difference between revisions

A '''computer file''' is a named collection of [[Data (computing)|data]] treated as a unit by the system that manages it. Today, this system is called a [[File system fragmentation|file system]]<ref name=":0" />. Many older computer systems lacked a distinct file system ''[[wikt:per se|per se]]'', yet a management [[software feature|feature]] is required in order to provide a file [[abstraction]].

 

Different [[File format|types of computer files]] are designed for different purposes. A file may be designed to store a written message, a [[document file format|document]], a [[spreadsheet]], an [[Digital image|image]], a [[Digital video|video]], a [[computer program|program]], or any wide variety of other kinds of data. Certain files can store multiple data types at once.

[[File:PunchCardDecks.agr.jpg|right|thumb|A [[punched-card]] file]]

"File" was used in the context of computer storage as early as January 1940. In ''Punched Card Methods in Scientific Computation'',<ref>{{Cite book |last1 =Eckert |first1 =W. J. |url =https://catalog.hathitrust.org/Record/002523225 |title =Punched card methods in scientific computation |last2 =Thomas J. Watson Astronomical Computing Bureau |first2 =New York |date =1940 |publisher =The Thomas J. Watson Astronomical Computing Bureau, Columbia University |location =New York |access-date=2018-04-17 |archive-date=2020-06-12 |archive-url =https://web.archive.org/web/20200612015646/https://catalog.hathitrust.org/Record/002523225 |url-status =live }}</ref> W. J. Eckert stated, "The first extensive use of the early Hollerith Tabulator in astronomy was made by [[Leslie Comrie|Comrie]].<ref>{{Cite journal |last =Comrie |first =L. J. |date =1928-04-13 |title=On the Construction of Tables by Interpolation (Plate 6) |journal =Monthly Notices of the Royal Astronomical Society |language =en |volume =88 |issue =6 |pages =506–523 |bibcode =1928MNRAS..88..506C |doi =10.1093/mnras/88.6.506 |issn =0035-8711 |doi-access=free}}</ref> He used it for building a table from successive differences, and for adding large numbers of harmonic terms". "Tables of [[Function (mathematics)|functions]] are constructed from their differences with great efficiency, either as printed tables or as a ''[https://hdl.handle.net/2027/uc1.b3621946?urlappend=%3Bseq=16 file of punched cards]''."

In February 1950, in a [[Radio Corporation of America]] (RCA) advertisement in ''[[Popular Science]]'' magazine<ref>{{Citation |title =Popular Science |date =February 1950 |url=https://books.google.com/books?id=9SwDAAAAMBAJ&pg=PA96 |page =96 |publisher=Bonnier Corporation |access-date=2014-03-07 |mode=cs1 |archive-date=2022-01-09 |archive-url =https://web.archive.org/web/20220109114611/https://books.google.com/books?id=9SwDAAAAMBAJ&pg=PA96 |url-status=live }}</ref> describing a new "memory" vacuum tube it had developed, RCA stated: "the results of countless computations can be kept 'on file' and taken out again.  Such a 'file' now exists in a 'memory' tube developed at RCA Laboratories. Electronically it retains figures fed into calculating machines, holds them in storage while it memorizes new ones – speeds intelligent solutions through mazes of mathematics."

In early computing usage, the word "file" could refer to the underlying [[computer hardware | hardware]], rather than to the contents stored on it. For example, the [[IBM 350]] disk drives were denominated "disk files".<ref>Martin H. Weik. Ballistic Research Laboratories Report #1115. March 1961. [https://ed-thelen.org/comp-hist/BRL61-ibm03.html#IBM-305-RAMAC pp. 314–331] {{Webarchive |url=https://web.archive.org/web/20161021113333/https://ed-thelen.org/comp-hist/BRL61-ibm03.html#IBM-305-RAMAC |date=2016-10-21 }}.</ref> The introduction, {{circa|1961}}, by the [[Burroughs MCP]] and the MIT [[Compatible Time-Sharing System]] of the concept of a "[[file system]]" that managed several virtual "files" on one storage device is the origin of the contemporary denotation of the word. Although the contemporary "[[register file]]" demonstrates the early concept of files, its use has greatly decreased.{{citation needed|date=August 2025}}

 

 

 

A [[file manager]] is a [[utility software |utility]] that allows a user to manipulate files directly. Typically, it allows one to move, create, delete and rename files and directories (a.k.a. folders), although it may not directly support viewing file content. Typically, a computer system has at least one file manager program for its native file system. For example, [[File Explorer]] is commonly used in Windows, and [[GNOME Files |Nautilus]] is in several [[Linux distribution]]s.

On most modern [[operating system]]s, files are organized into one-dimensional arrays of [[byte]]s.<ref>{{Cite web |title=The Unix File System |url=https://fsl.fmrib.ox.ac.uk/fslcourse/unix_intro/fstour.html |access-date=2026-04-11 |website=fsl.fmrib.ox.ac.uk}}</ref> The [[file format|format]] of a file is defined by its content since a file is solely a container for data.<ref>{{Cite web |title=Operating System: File System Management |url=https://www.vbspu.ac.in/e-content/File-System-Management.pdf}}</ref>

On some platforms the format is indicated by its [[filename extension]], specifying the rules for how the bytes must be organized and interpreted meaningfully. For example, the bytes of a plain text file ({{Mono|.txt}} in Windows) are associated with either [[ASCII]] or [[UTF-8]] characters, while the bytes of image, video, and audio files are interpreted otherwise. Most file types also allocate a few bytes for [[metadata]], which allows a file to carry some basic information about itself.{{citation needed|date=August 2025}}

Some file systems can store arbitrary (not interpreted by the file system) file-specific data outside of the file format, but linked to the file, for example [[extended attributes]] or [[Fork (file system)|forks]]. On other file systems this can be done via [[sidecar file]]s or software-specific databases. All those methods, however, are more susceptible to loss of metadata than [[Container format (computing)|container]] and [[archive file]] formats.{{citation needed|date=August 2025}}

File size is a measure of the storage space allocated to the file. Although often expressed in units of [[byte]]s, many older file systems tracked size in larger units such as [[disk sector |blocks]] or [[track (disk drive)|tracks]]. None-the-less, sometimes a more precise measure was available. For example, [[CP/M]] marked the end of a text file with [[Ctrl-Z]] which could be used to obtain a size with byte precision.

Typically, due to its design, a file system limits maximum file size.

When moving files between devices or partitions, some file managing software deletes each selected file from the source directory '''individually''' after being transferred, while other software deletes '''all files at once''' only after every file has been transferred.

For example, the <code>[[mv (Unix)|mv]]</code> command uses the former method when moving files individually with [[wildcard character|wildcards]] (example: <code>mv -n sourcePath/* targetPath</code>), but uses the latter method when moving entire directories (example: <code>mv -n sourcePath targetPath</code>).

Microsoft [[Windows Explorer]] also varies its approach: it uses the former method for [[mass storage]] file moves, but uses the latter method when transferring files via [[Media Transfer Protocol]], as described in {{section link|Media Transfer Protocol|File move behavior}}.

Many modern computer systems provide methods for protecting files against accidental and deliberate damage. Computers that allow for multiple users implement [[file permissions]] to control who may or may not modify, delete, or create files and folders. For example, a given user may be granted only permission to read a file or folder, but not to modify or delete it; alternatively, a user may be given permission to read and modify files or folders, but not to execute them. Permissions may also be used to allow only certain users to see the contents of a file or folder. Permissions protect against unauthorized tampering or destruction of information in files, and keep private information confidential from unauthorized users.

Any file that has any useful purpose must have some physical manifestation. A file (an abstract concept) in a real computer system must have a real physical analogue if it is to exist at all.