What determines the sequence in which a system checks devices for an operating system during bootup?

The sequence in which a system checks devices for an operating system during bootup is determined by the boot order. The boot order is a configuration setting in the system's BIOS or UEFI firmware that specifies the hierarchy of devices (such as hard drives, USB drives, or network adapters) from which the system should attempt to boot.

When a computer is powered on, it follows the boot order to find a device that contains a bootable operating system. If the first device in the boot order does not have a valid OS, the system will move to the next device in the order until it finds a suitable OS to load. This sequence is crucial because if a device with an OS is not prioritized correctly, the system may fail to boot or could boot incorrectly from an unintended source.

Other options, such as Secure Boot and various types of passwords, play roles in security or access control but do not directly influence the order in which devices are checked during the boot process.