The order of drives that a system s BIOS follows when looking for the operating system (OS) to boot after the computer has performed POST. For example, the BIOS may be instructed to first look to drive C (i.e., the hard disk) for the OS and then drive A (i.e., the floppy disk). If the OS is stored in drive C then the BIOS need look no further; however, if the BIOS does not find the OS in drive C then it will next look to drive A, and so on depending on the configuration of the boot sequence.
Users can change the order of the boot sequence through the CMOS setup.
