A diskette that contains a computer's minimal operating system and allows a PC to be started in emergencies, such as when a hard drive won't function normally. Also called a system or DOS diskette.
You can start your system from a diskette. To make a bootable diskette, insert a diskette in the diskette drive, type sys a: at the command line prompt, and press Enter. Use this bootable diskette if your system will not boot from the hard drive.