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File association: Wikis


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From Wikipedia, the free encyclopedia

A file association associates a file with an application capable of opening that file. More commonly, a file association associates a class of files (as determined by their filename extension, such as .txt) with a corresponding application (such as a text editor).


Associations and verbs

A single file extension may have several associations for performing various actions, also known as verbs. Some of the common verbs are:

  • open to open a file
  • edit to open a file for editing
  • print to print a file

A picture, for example, may be associated with these verbs so that open opens the picture in an image viewer, edit opens up an image editing program and print sends the picture to a printer.


Most operating systems support file associations in some form or the other. For example, opening a file from a file manager usually invokes the open verb in order to open the file with its associated application. Additional actions such as print are usually accessed via a right-click context menu. A mechanism for modifying associations is also usually present. An example for this is the Open With option in the Windows Shell.


Microsoft Windows

The Microsoft Windows series of operating systems, beginning with Windows 95 supports file extension-based associations. Associations are stored in registry as sets of verbs for each file extension. Older versions supported open associations stored in WIN.INI. File associations can be displayed and edited using the assoc command and with the help of the ftype command it is possible to create association between file type and application which will open files of this type. [1]

The Windows shell invokes file association actions through COM, drag and drop, command line calls or through Dynamic Data Exchange. Advanced features of Microsoft Windows file associations included manually defining a new file extension with any number of associated actions, a primary default action, showing extensions only for specific file types, customizing the file type icon and description and customizing associated MIME type and their handling (how to handle file types for files downloaded or directly opened from within the Internet Explorer browser). Advanced file association functionality however was removed in Windows Vista and later operating systems.[2]


Linux-based GUIs, such as KDE and GNOME, support MIME type-based associations. For example, the MIME type text/plain might be associated with a text editor.

Mac OS

Classic Mac OS used type codes and creator codes to associate each file with its corresponding application, regardless of file extension. The more recent Mac OS X also supports file extension–based associations.


See also


External links


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