1. A controller for controlling a machine tool comprising: means for executing a programmed machine cycle for generating output signals to control the machine tool to perform a plurality of operations, said programmed machine cycle comprising a plurality of sequences wherein each of said sequences defines an individual operation to be performed by the machine tool each of said sequences also being associated with a legend which describes said individual operation of said machine tool defined thereby; an input mechanism for selectively controlling the operation of said executing means between a run mode and a command mode, said run mode for automatically operating the machine tool through a complete programmed machine cycle and said command mode for manually stepping one sequence at a time through each of said sequences comprising a programmed machine cycle; a visual display operatively connected to said executing means for displaying a plurality of said legends; and means for highlighting at least one particular one of said plurality of legends displayed on said visual display wherein, when said run mode is selected, said particular highlighted legend is said legend associated with said sequence currently being performed and, when said command mode is selected, said particular highlighted legend is said legend associated with said next sequence to be performed.