Directory
From Free net encyclopedia
- This article is about the computing term. The Directory was also a government in revolutionary France from 1795 to 1799.
In computing, "Directory" can imply either of two distinct concepts: a file system directory or an information repository.
Contents |
File systems
In computing, a directory, catalog, or folder, is an entity in a file system which contains a group of files and other directories. A typical file system contains thousands of files, and directories help organize them by keeping related files together. A directory contained inside another directory is called a subdirectory of that directory. Together, the directories form a hierarchy, or tree structure.
If you imagine the computer's file system as a file cabinet, high–level directories may be represented by the drawers, while lower–level subdirectories may be represented as file folders within the drawers.
Historically, and even on some modern embedded devices, the filesystems either have no support for directories at all or only have a flat directory structure, meaning subdirectories are not allowed; there is only a group of top–level directories each containing files. The first popular fully general hierarchical filesystem was that of UNIX. This type of filesystem was an early research interest of Dennis Ritchie.
In modern times in Linux and other Unix-like systems, directory structure is defined by either the Filesystem Hierarchy Standard.
The folder metaphor
The name folder, presenting an analogy to the file folder used in offices, is common on some operating systems such as Mac OS and, increasingly, Microsoft Windows.
Strictly speaking, there is a difference between a directory which is a filing system concept, and the WIMP metaphor that is used to represent it (a folder).
Note that the folder metaphor may be misleading with regard to things like file permissions on UNIX: To rename or delete a file you need write permission to the directory that contains the file. This is perfectly understandable if the directory is seen as a list of filenames but not if it is seen as a container (as folder implies).
In graphical user interface (GUI) or WIMP environments, folders are often depicted with icons which resemble physical file folders such as those of a file cabinet in an office.
See also
Information repositories
The word directory is also used in computing and telephony with a different meaning: a repository or database of information. A directory, as opposed to a conventional database, is heavily optimized for reading, with the assumption that data updates are very rare compared to data reads. Commonly, a directory supports search and browsing in addition to simple lookups.
A website which offer access to a categorized listing of other websites optimized for lookup, search, or browsing is a directory, a web directory. The Open Directory Project is an example of a web directory.
Directory techology is often used in white page applications and network information services.
WHOIS is a prominent example of directory service providing white pages.
The Domain Name System (DNS) is a prominent example of directory service providing a network information service. DNS is also an example of a distributed hierarchical directory service that only has simple lookup capabilities.
The X.500 and LDAP directory services are examples of general-purpose distributed hierarchical object-oriented directory technologies. Both offer complex searching and browsing capabilities are used for white pages, network information services, public key infrastructure, and a wide range of other applications.
See also: database, directory service, web directory.cs:Adresář de:Verzeichnis es:Directorio fr:Répertoire (informatique) it:Directory nl:Directory ja:ディレクトリ pl:Katalog (informatyka) pt:Diretório uk:Директорія (інформаційні технології)