1. The part of a computer’s backing store where files are held.

2. The software system used to organize this. Files are abstract objects that must be mapped to physical sectors on magnetic disk or tape, optical disk, etc., and there are several organizational schemes to achieve this. MS-DOS and early versions of Windows used FAT (file allocation table), so called because it maintained all file-sector mappings in a single table. Modern versions of Windows still support FAT but for hard disks prefer the more sophisticated NTFS (NT file system). The Macintosh uses HFS Plus, the Unix file system (UFS) is widespread on UNIX, while there are several file systems available for Linux.