Updated: 12/16/2018 by Computer Hope
Series of binary 0 and 1 numbers.

Short for file allocation table, FAT is a method of keeping track of the contents of a hard drive used by early Microsoft operating systems that was first introduced in 1977. The table is a chart of numbers that correspond to cluster addresses on the hard drive. Below is a listing of the different types of FAT and the operating systems using them.


Today, later versions of Microsoft Windows, such as Windows XP, Vista, 7, and 10, are using NTFS (NTFS file system) and not FAT.


The oldest FAT, FAT8 was used on 8-inch floppies with the 8086 processor.


A File Allocation Table that uses 12-bit binary system that was derived from FAT8. A hard drive formatted using FAT12 can use a maximum of approximately 16,736,256 volume size, and today is no longer used. If your computer is running Windows 95 or above and fdisk displays FAT12, your hard drive is corrupt, bad, or has a virus.


FAT utilizing a 16-bit binary system. Used with Windows 3.x to Windows 95.


Enhanced File Allocation Table utilizing a 28-bit binary system, first used in Windows 95 OSR2 and Windows 98, that saves disk space using 4 k cluster. See FAT32 page for extended information about FAT32.

Computer acronyms, ExFat, Hard drive terms, HPFS, NTFS, Partition, UFS, VFAT