8.3

from The Free On-line Dictionary of Computing (8 July 2008)
8.3

   <file system, filename extension> A common shorthand for the
   limits on filename length imposed by the {file system} used by
   {MS-DOS} and {Microsoft Windows} - at most eight characters,
   followed by a ".", followed by a {filename extension} of at
   most three characters.

   {Windows 95} supports long filenames by using multiple
   directory entries per file.  The extra entries are hidden.  It
   also automatically derives an 8.3 name for each file for
   {backward compatibility} so that older versions of DOS can
   still access the file.

   (1998-10-05)