The FAT filesystem was created by Bill Gates and Marc McDonald in 1977 for managing disks in Microsoft Disk BASIC. In August 1980 Tim Paterson incorporated FAT into his 86-DOS operating system for the S-100 8086 CPU boards; the filesystem was the main difference between 86-DOS and its predecessor, CP/M.
The name originates from the usage of a table which centralizes the information about which areas belong to files, are free or possibly unusable, and where each file is stored on the disk. To reduce the management complexity, disk space is allocated to files in contiguous groups of hardware sectors called clusters. The maximum possible number of clusters has dramatically increased over time, and the number of bits required to identify a cluster is used to name the successive major versions of the format. The FAT standard has also evolved in several ways where backward compatibility with existing software has been preserved.