Preventing accidental erasing of data. Physical file protection is provided on the storage medium by turning a switch, moving a lever or covering a notch. Writing is prohibited even if the software directs the computer to do so. For example, on the eariler half-inch tape, a plastic ring in the center of the reel was removed (no ring-no write).
Logical file protection is provided by the operating system, which can designate files as read only. This allows both regular (read/write) and read only files to be stored on the same disk volume. Files can also be designated as hidden files, which makes them invisible to most software programs.
If You're Holey, You're Protected!
In the days of high-density 3.5" diskettes, when both holes were showing, you were "protected."