The FAT file system organizes data on both hard disks and floppy disks. If you have a FAT file system running on your computer, you have no doubt slammed up against its filename convention, lovingly referred to as 8.3 (pronounced “eight-dot-three”). This convention requires that a filename consist of no more than eight characters, followed by a separating period (.) and a filename extension of no more than three characters.
The main advantage of FAT volumes is that they can be accessed by MS-DOS, Microsoft Windows, and OS/2 systems. The FAT file system is currently supported on floppy disks and other removable media. The major disadvantages of FAT volumes are the limitations on the length and content of filenames and the lack of Unicode support. (Unicode is a character-encoding standard used worldwide, which helps to simplify the localization process.)
Valid FAT filenames have the following form:
[drive:][directory\]filename[.extension]
drive, which must be followed by a colon (:), specifies the name of an existing drive. It can be any letter from A through Z.
directory specifies which directory contains the file. It is separated from the filename by a backslash (\), and it must be either the full path, including the root directory, or the relative path from the current directory. A directory name contains no more than eight characters (and can have an optional three-character extension, preceded by a period) using any combination of letters, digits, and the following special characters:
$ % ` - _ @{ } ~ ` ! # ( )
filename consists of no more than eight letters, digits, and special characters. It can include embedded spaces if each space is preceded and followed by one or more legal characters. For example, the string disk 1 is a legal filename. Bear in mind, however, that although a space is a valid character in the FAT file system, many applications do not support spaces in filenames, so it's not a good idea to include them. Furthermore, FAT volumes do not distinguish between uppercase and lowercase letters; the filenames ALPHABET.DOC and alphabet.doc refer to the same file.
extension consists of no more than a total of three letters, digits, and special characters. It is preceded by a period.