With LFN support, filenames can be up to 255 characters long (excluding the NUL character). The period (.) is a valid filename character and can be used as many times as desired. The following special characters can also be used in LFNs.
: + , ; = [ ]
Blank spaces can be used anywhere in an LFN, but blank spaces and periods at the end of a filename are ignored. There is no requirement that LFN filenames have extensions; however, many applications still create and use them.
An LFN can be all uppercase, all lowercase, or mixed case. The case is preserved for directory listings but is ignored in file searches and all other system operations. Therefore, in a given directory, there cannot be more than one file with the same name when the only difference is case.