A file name that may have a large number of characters, including spaces, and use upper- and lower-case letters. Long filenames are now supported on most personal-computer operating systems. In earlier systems, the 8.3 system was common—files had a name of up to eight characters maximum, followed by a dot, followed by a file extension of up to three characters. For example, in this dictionary the file containing this entry is called ‘OUPCOM0L.XML’. On a long-filename system, it could be called ‘Oxford University Press Computing Dictionary letter L.XML file’.