This information was taken from MS TechNet
Whats FAT?
FAT may sound like a strange name for a file system, but its actually an acronym standing for file allocation table. Introduced in 1981, FAT is ancient in computer terms. Because of its age, most operating systemsincluding Windows NT, Windows 98, MacOS, and some versions of UNIXoffer support for FAT.
The FAT file system limits filenames to the 8.3 naming convention, meaning that a filename can have no more than eight characters before the period and no more than three characters after the period. Filenames in a FAT file system must also begin with a letter or number and cant contain spaces. Filenames arent case sensitive.
What about VFAT?
Perhaps youve also heard of a file system called VFAT. VFAT, which is an extension of the FAT file system, was introduced with Windows 95. VFAT maintains backward compatibility with FAT, but it relaxes the rules. For example, VFAT filenames can contain up to 255 characters, spaces, and multiple periods. Although VFAT preserves the case of filenames, it isnt considered case sensitive.
When you create a long filename (longer than 8.3) with VFAT, the file system actually creates two filenames. One is the actual long filename; this name is visible to Windows 95, Windows 98, and Windows NT (versions 4.0 and above). The second filename is a DOS alias, which is an abbreviated form of the long filename. The DOS alias is formed from the first six characters of the long filename (not counting spaces), a tilde, and a numeric trailer.
An interesting side effect results from the way VFAT stores long filenames. When you create a long filename with VFAT, it uses one directory entry for the DOS alias and another entry for each 13 characters of the long filename. In theory, a single long filename could occupy up to 21 directory entries. The root directory has a limit of 512 files, but if you were to use the maximum-length long filenames in the root directory, you could cut this limit to a mere 24 files. Therefore, you should use long filenames very sparingly in the root directory. Other directories arent affected by this limit.
Were discussing VFAT because its becoming more common than FAT. But aside from the differences weve mentioned, it has the same limitations. When you tell Windows NT to format a partition as FAT, it actually formats the partition as VFAT. The only time youll have a true FAT partition under Windows NT Version 4.0 is when you use another operating system (such as MS-DOS) to format the partition.
Whats FAT?
FAT may sound like a strange name for a file system, but its actually an acronym standing for file allocation table. Introduced in 1981, FAT is ancient in computer terms. Because of its age, most operating systemsincluding Windows NT, Windows 98, MacOS, and some versions of UNIXoffer support for FAT.
The FAT file system limits filenames to the 8.3 naming convention, meaning that a filename can have no more than eight characters before the period and no more than three characters after the period. Filenames in a FAT file system must also begin with a letter or number and cant contain spaces. Filenames arent case sensitive.
What about VFAT?
Perhaps youve also heard of a file system called VFAT. VFAT, which is an extension of the FAT file system, was introduced with Windows 95. VFAT maintains backward compatibility with FAT, but it relaxes the rules. For example, VFAT filenames can contain up to 255 characters, spaces, and multiple periods. Although VFAT preserves the case of filenames, it isnt considered case sensitive.
When you create a long filename (longer than 8.3) with VFAT, the file system actually creates two filenames. One is the actual long filename; this name is visible to Windows 95, Windows 98, and Windows NT (versions 4.0 and above). The second filename is a DOS alias, which is an abbreviated form of the long filename. The DOS alias is formed from the first six characters of the long filename (not counting spaces), a tilde, and a numeric trailer.
An interesting side effect results from the way VFAT stores long filenames. When you create a long filename with VFAT, it uses one directory entry for the DOS alias and another entry for each 13 characters of the long filename. In theory, a single long filename could occupy up to 21 directory entries. The root directory has a limit of 512 files, but if you were to use the maximum-length long filenames in the root directory, you could cut this limit to a mere 24 files. Therefore, you should use long filenames very sparingly in the root directory. Other directories arent affected by this limit.
Were discussing VFAT because its becoming more common than FAT. But aside from the differences weve mentioned, it has the same limitations. When you tell Windows NT to format a partition as FAT, it actually formats the partition as VFAT. The only time youll have a true FAT partition under Windows NT Version 4.0 is when you use another operating system (such as MS-DOS) to format the partition.
