File Systems

The numerals in the names FAT12, FAT16, and FAT32 refer to the number of bits required for a file allocation table entry.

  • FAT12 uses a 12-bit file allocation table entry (2 12 clusters).

  • FAT16 uses a 16-bit file allocation table entry (2 16 clusters).

  • FAT32 uses a 32-bit file allocation table entry. However, Windows 2000 reserves the first 4 bits of a FAT32 file allocation table entry, which means FAT32 has a theoretical maximum of 2 28 clusters.



FAT12 is only used on floppy disks and on very small volumes in Windows 2000.

There are additional relative advantages and disadvantages between FAT16 and FAT32.

Advantages of FAT16

Advantages of FAT16 include:

  • MS-DOS, Windows 95, Windows 98, Windows NT, Windows 2000, and some UNIX operating systems can use FAT16.

  • There are many software tools that can address problems and recover data on FAT16 volumes.

  • If you have a startup failure, you can start the computer by using an MS-DOS bootable floppy disk to troubleshoot the problem.

  • FAT16 is efficient, in speed and storage, on volumes smaller than 256 MB.

Disadvantages of FAT16

Disadvantages of FAT16 include:

  • The root folder can manage a maximum of 512 entries. The use of long file names (LFNs) can significantly reduce the number of available entries.

  • FAT16 is limited to 65,536 clusters, but because certain clusters are reserved, it has a practical limit of 65,524. The largest FAT16 volume on Windows 2000 is limited to 4 GB and uses a cluster size of 64 KB. To maintain compatibility with MS-DOS, Windows 95, and Windows 98, a volume cannot be larger than 2 GB.

  • FAT16 is inefficient on larger volume sizes, as the size of the cluster increases. The space allocated for storing a file is based on the size of the cluster allocation granularity, not the file size. For example, a 10-KB file stored on a 1.2-GB volume, which uses a 32-KB cluster, wastes 22 KB of disk space.

  • The boot sector is not backed up.

  • There is no built-in file system security or compression scheme with FAT16.

Advantages of FAT32

FAT32 has the following enhancements:

  • The root folder on a FAT32 drive is an ordinary cluster chain and can be located anywhere on the volume. For this reason, FAT32 does not restrict the number of entries in the root folder.

  • FAT32 uses smaller clusters (4 KB for volumes up to 8 GB), so it allocates disk space more efficiently than FAT16. Depending on the size of your files, FAT32 creates the potential for tens and even hundreds of megabytes of additional free disk space on larger volumes compared to FAT16.

  • FAT32 can automatically use the backup copy of the file allocation table instead of the default copy (with FAT16, only a disk repair tool such as Chkdsk can implement the backup).

  • The boot sector is automatically backed up at a specified location on the volume, so FAT32 volumes are less susceptible to single points of failure than FAT16 volumes.

Disadvantages of FAT32

Disadvantages of FAT32 include:

  • The largest FAT32 volume that Windows 2000 can format is 32 GB.

  • FAT32 volumes are not directly accessible from operating systems other than Windows 95 OSR2 and Windows 98.

  • If you have a startup failure, you cannot start the computer by using an MS-DOS or Windows 95 (excluding version OSR2 and later) bootable floppy disk.

  • There is no built-in file system security or compression scheme with FAT32.