(This article is a less technical introduction to the subject. For the main encyclopedia article, see Design of the FAT file system.) File Allocation Table (FAT) is a file system developed for personal computers. Originally developed in 1977 for use on floppy disks, it was adapted for use on hard disks and other devices. It is often supported for compatibility reasons by current operating systems for personal computers and many mobile devices and embedded systems, allowing interchange of data between disparate systems. The increase in disk drives capacity required three major variants: , and . The FAT standard has also been expanded in other ways while generally preserving backward compatibility with existing software.