High Quality Content by WIKIPEDIA articles! File Allocation Table (FAT) is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of their relative simplicity. FAT was also commonly used on hard disks throughout the DOS and Windows 9x eras, but its use on hard drives has declined since the introduction of Windows XP, which primarily uses the newer NTFS.