FAT File System

The File Allocation Table (FAT) file system organizes data on fixed disks and floppy disks. The distinguishing feature of the FAT file system is its file name convention. The file name convention consists of a file name (up to eight characters), a separating period (.), and a file name extension (up to three characters).

The main advantage of FAT volumes is that they are accessible by MS-DOS, Microsoft® Windows®, and OS/2 systems. FAT is also the only file system currently supported on floppy disks and other removable media.

Valid FAT file names have the following form:

[[drive:]][[directory\]]filename[[.extension]]

The drive parameter must name an existing drive and can be any letter from A through Z. The drive letter must be followed by a colon (:).

The directory parameter specifies the directory that contains the file's directory entry. This value must be followed by a backslash (\) to separate it from the file name. If the specified directory is not in the current directory, directory must include the names of all directories in the file's path, separated by backslashes. The root directory is specified by using a backslash at the beginning of the name. For example, if the directory ABCD is in the directory SAMPLE and SAMPLE is in the root directory, the correct directory specification is \SAMPLE\ABCD. A directory name consists of any combination of up to eight letters, digits, or the following special characters:

$ % ' – _ @ { } ~ ` ! # ( )

A directory name can also have an extension that is any combination of up to three letters, digits, or special characters, preceded by a period (.).

The filename and extension parameters specify the file. Filename can be any combination of up to eight letters, digits, or the special characters previously listed; extension can be any combination of up to three letters, digits, or special characters, all preceded by a period. Filename can also include embedded (preceded and followed by one or more letters, digits, or special characters just noted) spaces. For example, the string "disk 1" is a valid value for filename.

FAT volumes do not distinguish between uppercase and lowercase letters.