FAT is an acronym for file access (or allocation) table. This is a table that the operating system of a computer uses to locate files on a disk.

The FAT was designed and developed by Bill Gates. Gates developed the FAT for a version of Basic that could store programs and data on floppy disks. The design was incorporated in an early version of the operating system for the Intel 8086 chip. Gates purchased the rights to this operating system and rewrote it to create the first version of DOS. The subsequent ramifications to computing and to Gate's success have been enormous.

A file may not be stored contiguously. Due to fragmentation, a file may be divided into many sections that are scattered around the disk. It is the task of the FAT to keep track of all the information. FATs themselves are...