14 DAY TRIAL // Wikipedia says that a FAT file (File Allocation Table ) is a patented file system that was developed by Microsoft for MS-DOS and is the primary file system for consumer versions of Microsoft Windows up to and including Windows Me. The FAT file system is considered relatively uncomplicated, and because of that, it is a popular format for floppy disks; moreover, it is supported by virtually all existing operating systems for personal computers, and because of that, it is often used to share data between several operating systems booting on the same computer (a multiboot environment).
It is also used on solid-state memory cards and other similar devices. The most common implementations have a serious drawback in that when files are deleted and new files written to the media, their fragments tend to become scattered over the entire media making reading and writing a slow process.
This has recently become important because of the fact that after two years of battling, the U.S. Patent and Trademark Office has upheld and validated Microsoft's claim on the two FAT file system patents. Unlike last year when they had previously rejected the two patents, the Patent Office re-examined the case at the request of a public interest group called the Public Patent Foundation in April 2004, and turned their decision around. These submitted patents can indeed become patentable.
The problem is that FAT files are used with nearly everything: Windows operating system, removable flash memory cards, Linux/Unix products; it's also a common file system used to transfer data with Windows. Under the terms of the Free Software Foundation's General Public License, Linux cannot be distributed if it contains patented technology that requires royalty payments. If Microsoft pursues with the patents, they could essentially try to seek royalties. This would be disastrous for Linux since they're on of Microsoft's biggest competitors.
The FAT filesystem was invented in 1977 for managing disks in Microsoft Disk BASIC by Bill Gates and Marc McDonald. It was incorporated by Tim Paterson in August 1980 to his 86-DOS operating system. The filesystem was the main difference between 86-DOS and CP/M, of which 86-DOS was otherwise mostly a clone.
There are some that argue that the decision to attribute Microsoft the patents is faulty since it was not created for Microsoft, but rather as a part of DOS. In any case, it will be interesting to see how this whole process will play itself out. If Microsoft truly decides to seek royalties against an upcoming competitor, then it could be curtains for the Linux guys.