A memory card and apparatus used therewith. The memory card comprises a rectangular card body having terminals in the vicinity of one end and a storage device disposed in the card body for storing data. A switch on the card is operable to a state to prevent stored data from being erased; and a status signal representing the state of the switch is supplied to one or more of the terminals. The apparatus with which the card is used has mating terminals to receive the status signal. Depending upon the state of that status signal, the apparatus is selectively inhibited from writing data to the memory card or erasing data stored in the memory card.