A surgical end effector can comprise a first jaw, a staple cartridge supported by the first jaw, wherein the staple cartridge comprises a plurality of staples removably stored therein, a second jaw comprising an anvil, wherein the second jaw is rotatable relative to the first jaw between an open position and a closed position, and wherein the anvil is configured to deform the staples when the staples are deployed from the staple cartridge. The surgical end effector can further comprise a sensor configured to detect when the anvil is in its closed position. The second jaw can be rotatable relative to the first jaw toward a closed position and the surgical end effector can comprise detection means for detecting if the anvil is in its closed position.
