The boot sequence (sometimes called BIOS boot order or BIOS boot sequence) is the order of devices in the BIOS that the computer searches for an operating system.

Although a hard drive is typically the primary device a user wants to boot from, other devices such as optical drives, floppy drives, flash drives, and network resources are typically listed as boot order options in the BIOS.

On many computers, the hard drive is listed as the first item in the boot order. Because the hard drive is always a bootable device (unless the computer has a major problem), you will need to change the boot order if you want to boot from something else, such as a DVD or a flash drive.

Some devices will instead list something like optical drive first, but hard drive second. In this scenario, you don't need to change the boot order to boot from just the hard drive unless there is actually a disk in the drive with boot files on it. If there is no disk, simply wait for the BIOS to skip the optical drive and look for the operating system in the next entry, which in this example would be the hard drive.