A surgical instrument system, comprising: a housing, comprising: an electric motor; a first shaft attachable to said housing, comprising: a first end effector, comprising: a first anvil; and a first staple cartridge; a first drive system configured to perform a first end effector function, wherein said first end effector function comprises moving said first anvil toward said first staple cartridge, wherein said first drive system is operably engageable with said electric motor, and wherein said electric motor is operated a first number of rotations to perform said first end effector function; and a first end-of-stroke sensor configured to determine when said first anvil is in a first closed position, wherein said first end-of-stroke sensor is configured to stop said electric motor when said first anvil is in said first closed position; and a second shaft attachable to said housing in lieu of said first shaft, said second shaft comprising: a second end effector, comprising: a second anvil; and a second staple cartridge; a second drive system configured to perform a second end effector function, wherein said second end effector function comprises moving said second anvil toward said second staple cartridge, wherein said second drive system is operably engageable with said electric motor, wherein said electric motor is operated a second number of rotations to perform said second end effector function, and wherein said first number of rotations is different than said second number of rotations; and a second end-of-stroke sensor configured to determine when said second anvil is in a second closed position, wherein said second end-of-stroke sensor is configured to stop said electric motor when said second anvil is in said second closed position, and wherein said first closed position is different than said second closed position. a housing, comprising: an electric motor; a first shaft attachable to said housing, comprising: a first end effector, comprising: a first anvil; and a first staple cartridge; a first drive system configured to perform a first end effector function, wherein said first end effector function comprises moving said first anvil toward said first staple cartridge, wherein said first drive system is operably engageable with said electric motor, and wherein said electric motor is operated a first number of rotations to perform said first end effector function; and a first end-of-stroke sensor configured to determine when said first anvil is in a first closed position, wherein said first end-of-stroke sensor is configured to stop said electric motor when said first anvil is in said first closed position; and a first end effector, comprising: a first anvil; and a first staple cartridge; a first anvil; and a first staple cartridge; a first drive system configured to perform a first end effector function, wherein said first end effector function comprises moving said first anvil toward said first staple cartridge, wherein said first drive system is operably engageable with said electric motor, and wherein said electric motor is operated a first number of rotations to perform said first end effector function; and a first end-of-stroke sensor configured to determine when said first anvil is in a first closed position, wherein said first end-of-stroke sensor is configured to stop said electric motor when said first anvil is in said first closed position; and a second shaft attachable to said housing in lieu of said first shaft, said second shaft comprising: a second end effector, comprising: a second anvil; and a second staple cartridge; a second drive system configured to perform a second end effector function, wherein said second end effector function comprises moving said second anvil toward said second staple cartridge, wherein said second drive system is operably engageable with said electric motor, wherein said electric motor is operated a second number of rotations to perform said second end effector function, and wherein said first number of rotations is different than said second number of rotations; and a second end-of-stroke sensor configured to determine when said second anvil is in a second closed position, wherein said second end-of-stroke sensor is configured to stop said electric motor when said second anvil is in said second closed position, and wherein said first closed position is different than said second closed position. a second end effector, comprising: a second anvil; and a second staple cartridge; a second anvil; and a second staple cartridge; a second drive system configured to perform a second end effector function, wherein said second end effector function comprises moving said second anvil toward said second staple cartridge, wherein said second drive system is operably engageable with said electric motor, wherein said electric motor is operated a second number of rotations to perform said second end effector function, and wherein said first number of rotations is different than said second number of rotations; and a second end-of-stroke sensor configured to determine when said second anvil is in a second closed position, wherein said second end-of-stroke sensor is configured to stop said electric motor when said second anvil is in said second closed position, and wherein said first closed position is different than said second closed position.