Before you start up the Apple IIGS System Disk and begin learning about the Finder, you should write-protect the system disk. Write-protecting a disk prevents the information on the disk from being changed accidentally. It's a good idea to write-protect any disks that contain information you don't want to change.
To write-protect the system disk, simply slide the tab to uncover the square opening in the corner of the disk.
Figure 2-6 Write-protecting a disk
Session 2: An introduction to the Finder