The portion of a filename, following the final point, which indicates the kind of data stored in the file – the file type.
Many operating systems use filename extensions, e.g. Unix, VMS, MS-DOS, Microsoft Windows. They are usually from one to three letters (some sad old OSes support no more than three). Examples include “c” for C source code, “ps” for PostScript, “txt” for arbitrary text.
NEXTSTEP and its descendants also use extensions on directories for a similar purpose.
Apart from informing the user what type of content the file holds, filename extensions are typically used to decide which program to launch when a file is “run”, e.g. by double-clicking it in a GUI file browser. They are also used by Unix’s make to determine how to build one kind of file from another.
Compare: MIME type.
Tony Warr’s comprehensive list (http://camalott.com/~rebma/filex.html).
FAQS.org Graphics formats (http://faqs.org/faqs/graphics/fileformats-faq/).
[fi-leen, fahy-] /fɪˈlin, faɪ-/ noun 1. Edward Albert, 1860–1937, U.S. retail merchant.
storage A system for storage of images on laser disk using COLD. (1995-11-09)
[fi-ley, fee-ley] /fɪˈleɪ, ˈfi leɪ/ noun, New Orleans Cookery. 1. a powder made from the ground leaves of the sassafras tree, used as a thickener and to impart a pungent taste to soups, gumbos, and other dishes. /faɪl/ noun 1. a folder, box, etc, used to keep documents or other items in order 2. the […]
[fahyl] /faɪl/ noun 1. a folder, cabinet, or other container in which papers, letters, etc., are arranged in convenient order for storage or reference. 2. a collection of papers, records, etc., arranged in convenient order: to make a file for a new account. 3. Computers. a collection of related data or program records stored on […]