Duncan and Law present a concise introduction to the theory and program documentation of a powerful computer-aide general-shape machining system called POLYHEDRAL NC. POLYHEDRAL NC and its accompanying programs provide a well-proven system of IBM compatible microcomputer software for both defining graphically, and replicating by machining, piece-wise analytical and measured physical surfaces. All aspects of graphics are treated via one universal program, TRUEPERS. Machining is executed under control of either of two other general programs incorporating powerful anti-interference features. This system can reproduce accurately a wide range of complex highly variable surfaces, from human prostheses to machine dies.