Disk formatting is the process of preparing a hard disk or other storage medium for use, including setting up an empty file system. A variety of utilities and programs exist for this task; pictured to the right is the iconic FORMAT.COM of MS-DOS and PC-DOS.
Large disks can be partitioned, divided into logical sections that are formatted with their own file systems. This is normally only done on hard disks because of the small sizes of other disk types, as well as compatibility issues.
A corrupted operating system can be reverted to a clean state by formatting the disk and reinstalling the OS, as a drastic way of combatting a software problem or malware infection. Obviously, important files should be backed up beforehand.