A surgical instrument system, comprising: a handle, comprising: an electric motor; and an actuator configured to operate said electric motor; a first shaft attachable to said handle, comprising: a first end effector, comprising a first anvil and a first staple cartridge; and a first drive system configured to perform a first end effector function, wherein said first drive system is operably engageable with said electric motor, and wherein said electric motor is operated in a first direction to perform said first end effector function; and a second shaft attachable to said handle in lieu of said first shaft, said second shaft comprising: a second end effector, comprising a second anvil and a second staple cartridge; and a second drive system configured to perform a second end effector function, wherein said second drive system is operably engageable with said electric motor, wherein said electric motor is operated in a second direction to perform said second end effector function, wherein said first end effector function comprises moving said first anvil toward said first staple cartridge, wherein said second end effector function comprises moving said second anvil toward said second staple cartridge, and wherein said second direction is opposite said first direction; wherein the surgical instrument system is characterised in that: the handle includes at least one sensor configured to detect whether the first or second shaft has been attached to the handle and communicate this information to a microprocessor, wherein the microprocessor is configured such that when the actuator is actuated to perform the first or second end effector function, the microprocessor rotates the electric motor in the first direction or the second direction depending on whether the first shaft or the second shaft respectively has been attached to the handle. a handle, comprising: an electric motor; and an actuator configured to operate said electric motor; an electric motor; and an actuator configured to operate said electric motor; a first shaft attachable to said handle, comprising: a first end effector, comprising a first anvil and a first staple cartridge; and a first drive system configured to perform a first end effector function, wherein said first drive system is operably engageable with said electric motor, and wherein said electric motor is operated in a first direction to perform said first end effector function; and a first end effector, comprising a first anvil and a first staple cartridge; and a first drive system configured to perform a first end effector function, wherein said first drive system is operably engageable with said electric motor, and wherein said electric motor is operated in a first direction to perform said first end effector function; and a second shaft attachable to said handle in lieu of said first shaft, said second shaft comprising: a second end effector, comprising a second anvil and a second staple cartridge; and a second drive system configured to perform a second end effector function, wherein said second drive system is operably engageable with said electric motor, wherein said electric motor is operated in a second direction to perform said second end effector function, wherein said first end effector function comprises moving said first anvil toward said first staple cartridge, wherein said second end effector function comprises moving said second anvil toward said second staple cartridge, and wherein said second direction is opposite said first direction; a second end effector, comprising a second anvil and a second staple cartridge; and a second drive system configured to perform a second end effector function, wherein said second drive system is operably engageable with said electric motor, wherein said electric motor is operated in a second direction to perform said second end effector function, wherein said first end effector function comprises moving said first anvil toward said first staple cartridge, wherein said second end effector function comprises moving said second anvil toward said second staple cartridge, and wherein said second direction is opposite said first direction; wherein the surgical instrument system is characterised in that: the handle includes at least one sensor configured to detect whether the first or second shaft has been attached to the handle and communicate this information to a microprocessor, wherein the microprocessor is configured such that when the actuator is actuated to perform the first or second end effector function, the microprocessor rotates the electric motor in the first direction or the second direction depending on whether the first shaft or the second shaft respectively has been attached to the handle.