Definitions for "Startup Disk"
Keywords:  floppy, disk, boot, reformatting, drive
A disk used to start up the computer.
system software: 1. A Control Panel that you use to designate which disk the Mac will use to start up (load and run the operating system and the Finder). This situation exists when there are multiple hard drives containing System Folders connected a Mac. The startup volume's icon will appear in the top-right corner of the desktop. 2. (lower case) Any floppy or hard drive that has a System Folder on it that you can use to get your Mac started.
The disk which contains the active system software loaded at startup.