An apparatus comprising: an end effector having a first and second jaw (72,76) for clamping a material therebetween, and a staple for stapling the material clamped between the first and second jaw (72,76); a drive system operatively coupled to the end effector by one or more driving mechanisms such that driving an actuator of the drive system articulates the end effector, wherein the drive system can move the first jaw toward the second jaw so as to clamp the material between the jaws (72,76) at a clamping force, and wherein the drive system is coupled to the staple such that driving the actuator to staple produces a firing force so as to fire the staple into the material clamped between the first and second jaws (72,76); a sensor for monitoring a drive parameter of the actuator when the actuator induces the clamping force and/or the firing force and detecting a displacement of the actuator; a processor configured for determining an indicator of success or failure of clamping or staple firing in response to the monitored drive parameter, the drive parameter comprising a torque or a force, wherein the indicator is of failure when the drive parameter during clamping is outside of an acceptable range of desired drive parameters for clamping or when the drive parameter during firing is outside an acceptable range of desired drive parameters for firing, and a user interface configured to communicate the indicator of success or failure of clamping or firing, to a user, said apparatus being characterized in that the acceptable range of desired drive parameters varies with the displacement of the actuator. an end effector having a first and second jaw (72,76) for clamping a material therebetween, and a staple for stapling the material clamped between the first and second jaw (72,76); a drive system operatively coupled to the end effector by one or more driving mechanisms such that driving an actuator of the drive system articulates the end effector, wherein the drive system can move the first jaw toward the second jaw so as to clamp the material between the jaws (72,76) at a clamping force, and wherein the drive system is coupled to the staple such that driving the actuator to staple produces a firing force so as to fire the staple into the material clamped between the first and second jaws (72,76); a sensor for monitoring a drive parameter of the actuator when the actuator induces the clamping force and/or the firing force and detecting a displacement of the actuator; a processor configured for determining an indicator of success or failure of clamping or staple firing in response to the monitored drive parameter, the drive parameter comprising a torque or a force, wherein the indicator is of failure when the drive parameter during clamping is outside of an acceptable range of desired drive parameters for clamping or when the drive parameter during firing is outside an acceptable range of desired drive parameters for firing, and a user interface configured to communicate the indicator of success or failure of clamping or firing, to a user, said apparatus being characterized in that the acceptable range of desired drive parameters varies with the displacement of the actuator.