<operating system> A program on a hard disk, floppy disk or other media, which is loaded when the computer is turned on or rebooted and which controls the next phase of loading the actual operating system. The loading and execution of the boot block is usually controlled by firmware in ROM or PROM. It may be at some fixed location possibly or may be pointed to by the master boot record.
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Nearby terms: Boole, George « Booster « boot « boot block » boot disk » booting » BOOTP