[W/K] :: Filename extension

  filename extension
       n : a string of characters beginning with a period and followed
           by one to three letters; the optional second part of a PC
           computer filename; "most applications provide extensions
           for the files they create"; "most BASIC files use the
           filename extension .BAS" [syn: extension, file name
           extension]

  filename extension
       
           The portion of a filename, following the
          final point, which indicates the kind of data stored in the
          file.
       
          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://www.faqs.org/faqs/graphics/fileformats-faq/).
       
          (2002-04-19)