Alternatively referred to as a startup disk or boot disk, a bootable disk contains special files required for the computer to boot into an operating system. If the bootable disk is removable media like a floppy diskette or CD-ROM, it usually bypasses the hard drive, depending on the settings in the BIOS. Commonly this diskette is used to troubleshoot the computer or allow the user to copy files when a computer is down.
A "bootable disk" refers to a floppy diskette. If you're referring to a CD or DVD, it may be referred to as a "boot disc" or "restore disc."
What is a "no bootable disk" error?
If the computer has no bootable media, or is trying to boot from media which does not contain a functioning boot record, the error No bootable disk or No bootable device is displayed. For information about non-booting computers or disks, see our bootable device guide.