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.