An 8.3 filename (also called a short filename or SFN) is a filename convention used by old versions of DOS, versions of Microsoft Windows prior to Windows 95, and Windows NT 3.51.
Short filenames are limited to at most eight characters (after any directory specifier), followed optionally by a filename extension consisting of a period . and at most three further characters. For systems that only support 8.3 filenames, excess characters are ignored and if a file name has no extension, the ., if present, has no significance (that is, myfile and myfile. are equivalent). Furthermore, in these systems file and directory names are uppercase, although systems that use the 8.3 standard are usually case-insensitive (hence CamelCap.tpu will be equivalent to the name CAMELCAP.TPU). However, on non-8.3 Operating Systems (such as almost any modern Operating System) accessing 8.3 File Systems (including DOS-formatted diskettes, but also including some modern memory cards and networked file systems) the underlying system may alter filenames internally to preserve case and avoid truncating letters in the names, for example in the case of VFAT.
Source: Wikipedia
