write protect
A feature of certain removable media storage devices that tells the system whether or not it should allow the data on the media to be modified. Write protecting an item of media prevents accidental overwriting of valuable data.
For example, the write protect tab on a 3.5-inch floppy disks is a small sliding plastic square that can either cover or expose a hole near the edge of the disk cover. The drive wil only allow the disk to be written to if the hole is closed.