Startup Disk control panel

The Startup Disk control panel (formerly Startup Device) was provided by Apple Computer to allow users to select their preferred startup disk in classic Mac OS.

Usage
For users of classic Mac OS, this control panel was useful for Macs containing, or attached to, more than one bootable drive, such as a CD-ROM, floppy drive, or hard drive. The first (or selected) icon in this control panel represents the volume containing a System Folder that will be loaded upon the next reboot. A different startup disk can be selected by clicking a another icon. This method was sometimes used to boot from a system installer disk (such as a CD-ROM) instead of the default internal drive. On a Macintosh Centris 610 or newer Mac, an alternate method to boot from the CD-ROM drive was to simply hold down the "C" button while starting up.

History
The control panel first appeared as "Startup Device" in October 1987, which could be accessed through the Control Panel desk accessory of System 4.2 to support the Macintosh SE and II, which were the first Macs to contain more than one internal drive. Earlier versions of the system software would automatically default to the floppy drive instead of the hard drive if a bootable floppy disk was inserted, but the Macintosh SE and II were both available in dual floppy versions. The Macintosh II also had sufficient space to more than one internal SCSI drive.

Starting in System 7, released in May 1991, "Startup Device" was renamed to "Startup Disk", which became a separately-launchable control panel of its own. Multiple drives became more commonplace in large tower configurations, such as the Macintosh Quadra 900.

Transition to Mac OS X
Before Mac OS X arrived, there were few cases of installing more than one System Folder on a single un-partitioned hard drive. Versions of the Startup Disk control panel prior to Mac OS 9.1 recognized only one "blessed" System Folder per volume. The version of Startup Disk included with Mac OS 9.1 recognized, for the first time in Macintosh history, more than one System Folder on one hard drive, thus enabling users to switch between different versions of the Mac OS, including Mac OS X, on the same volume. Networked drives were also supported.

In Mac OS X, this control panel was superseded by the Startup Disk preference pane of the System Preferences utility.