How does the BIOS load the system boot program from a floppy disk?

Source: Internet
Author: User

How does the BIOS load the system boot program from a floppy disk? When the computer's power is turned on, it will perform some self-check (POST) and then look for the boot disk. If you choose to start from a floppy disk, the computer will check the disk's 0-sided 0-Track 1-sector. If it finds that it uses 0xAA55 (assuming we regard this sector as a character array sector, for, this end mark is equivalent to sector [510] = 0x55, and sector [511] = 0xAA), then the BIOS considers it as a boot sector, that is, the Boot Sector. Of course, in addition to ending with 0xAA55, a correct Boot Sector should also contain an Execution Code of less than 512. Once the BIOS finds the Boot Sector, it will load the 512B content to the 0000: 7C00 of the memory, then jump to 0000: 7C00, and submit the Controller to this Guide code. So far, the computer is no longer controlled by the programs inherent in the BIOS, but is controlled by a part of the operating system.

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