IBM R30 Operator's Manual page 31

Setting the Write-Protect Tab on 3.5-Inch Diskettes
Setting the write-protect tab on a diskette is necessary so that information is not accidentally
lost. When the write-protect tab is set (slot open) on a diskette, information can be read from
the diskette but cannot be written to it.
There is a write-protect tab on the 3.5-inch diskette.
To locate the write-protect tab, turn the diskette over with the label facing down.
To prevent writing to a diskette, slide the write-protect tab to open the slot.
Diskette with Write-Protect Tab Set
Rear View
To allow writing to a diskette, slide the write-protect tab to close the slot.
Diskette with Write-Protect Tab Not Set
Rear View
(Slot Open)
Write-Protect Tab
(Slot Closed)
Write-Protect Tab
2-11
Using the CPU Enclosure