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The magnetic disk (usually a hard disk)from which an operating system kernel is loaded (or"bootstrapped"). This second phase in system start-up isperformed by a simple bootstrap loader program held in ROM,possibly configured by data stored in some form of writablenon-volatile storage.MS-DOS and Microsoft Windows can be configured (in theBIOS) to try to boot off either floppy disk or harddisk, in either order. By default they first check for thepresence of a floppy disk in the drive at start-up and tryto use that as a boot disk if present. If no disk is in thedrive they then try to boot off the hard disk.Some operating systems, notably SunOS and Solaris, canbe configured to boot from a network rather than from disk.Such a system can thus run as a diskless workstation.