)To mark a file or disk so that its contents cannot be modified or deleted. When you want to make sure that neither you nor another user can destroy data, you can write-protect it. Many operating systems include a command to write-protect files. You can also write-protect 5¼-inch floppy disks by covering the write-protect notch with tape. 3½-inch floppy diskettes have a small switch that you can set to turn on write-protection.