Именование файлов 8.3 в DOS и Windows

Filename convention used by old versions of DOS and Windows
An 8.3 filename (also called a short filename or SFN) is one that obeys the filename convention used by old versions of DOS and versions of Microsoft Windows prior to Windows 95 and Windows NT 3.5. It is also used in modern Microsoft operating systems as an alternate filename to the long filename, to provide compatibility with legacy programs. The filename convention is limited by the FAT file system. Similar 8.3 file naming schemes have also existed on earlier CP/M, TRS 80, Atari, and some Data General and Digital Equipment Corporation minicomputer operating systems.

8.3 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. If a file name has no extension, a trailing has no significance (that is, and are equivalent). Furthermore, file and directory names are uppercase in this system, even though systems that use the 8.3 standard are usually case insensitive (making equivalent to the name ). However, on non 8.3 operating systems (such as almost any modern operating system) accessing 8.3 file systems (including DOS formatted floppy disks, 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.

This legacy technology is used in a wide range of products and devices, as a standard for interchanging information, such as compact flash cards used in cameras. VFAT LFN long filenames introduced by Windows 95/98/ME retained compatibility. But the VFAT LFN used on NT based systems (Windows NT/2K/XP) uses a modified 8.3 shortname. If a filename contains only lowercase letters, or is a combination of a lowercase basename with an uppercase extension, or vice versa; and has no special characters, and fits within the 8.3 limits, a VFAT entry is not created on Windows NT and later versions such as XP. Instead, two bits in byte 0x0c of the directory entry are used to indicate that the filename should be considered as entirely or partially lowercase. Specifically, bit 4 means lowercase extension and bit 3 lowercase basename, which allows for combinations such as or but not Few other operating systems support this. This creates a backward compatibility filename mangling problem with older Windows versions (95, 98, ME) that see all uppercase filenames if this extension has been used, and therefore can change the capitalization of a file when it is transported, such as on a USB flash drive. This can cause problems for operating systems that do not exhibit the case insensitive filename behavior as DOS and Windows do. Linux will recognize this extension when reading; the mount option shortname determines whether this feature is used when writing. For MS DOS you may use Henrik Haftmann's DOSLFN.