1. A method for detecting the presence of a workpiece characteristic and controlling the execution sequence of operational steps in a machining program being stored in a control connected to a machine, said machine having machine slides moving along axes of motion in response to the machining program to effect relative motion between a workpiece and a tool holder having a cutting tool and a sensing element selectively associated therewith, the method comprising the steps of: (a) storing in association with the machining program (1) first instructions for defining a scanning cycle to cause the sensing element to detect the presence of a workpiece characteristic, (2) second instructions to test for the presence of the workpiece characteristic to determine the sequence of execution of subsequent operational steps in the machining program, and (3) third instructions defining a nonsequential location in the machining program associated with a particular operational step; (b) executing the scanning cycle in response to the first instruction to produce a condition signal having a first state in response to the sensing element detecting the workpiece characteristic and having a second state in response to a failure of the sensing element to detect the workpiece characteristic; (c) testing the state of the condition signal in response to the second instructions; and (d) controlling the sequence of execution of the operational steps in the machining program in response to the state of the condition signal and the third instructions.