File Allocation Table (FAT) is a partially patented file system developed by Microsoft for DOS and was the primary file system for consumer versions of Microsoft Windows up to and including Window ME. FAT as it applies to flexible/ floppy and optical disk cartridges (FAT 12 and FAT 16 without long file name support) .

History of FAT:

The FAT file systems  was created by Bill Gates and Marc McDonald in 1977 for managing disks in Microsft Disk BASIC. In August 1980 Tim Paterson incorporated FAT into is 86-DOS operating system for the S-100 8086 CPU boards; the filesystem was the main difference between 86-DOS and is redecessor, CP/M

The name originates from the usage of a table which centralizes the information about which areas belong to files, are free or possible unusavel, and the where each file 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 had 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 serveral ways where backward compatibility with existing software has been preserved.