An apparatus and method for sampling input data to a computer which is controlling the operations of a machine tool. A general purpose digital computer is used to provide servo control signals to the various machine tool slides. The output digital signals of the computer are converted to analog signals by digital to analog converters and fed in the machine tool servo valves which, in turn, control servomotors which, in turn, drive the machine tool slides. Data is sent back to the computer from feedback transducers which are operably connected to the machine tool slides. Means are provided between the feedback transducers and the computers for passing a sampling of the feedback data at periodic intervals. The computer is programmed to request data from the particular feedback device at these intervals. The computer compares this sample of feedback data with the next previous sample of feedback data. This comparison tells the computer the direction, distance, and at what velocity the machine tool slide has moved.