1 ) A plastic injection molding machine comprising: a screw within a barrel and a screw injector mechanism for axially translating said screw within said barrel to inject a shot of melt into a mold; a clamp containing a mold separable along a parting line and a clamp mechanism for opening, closing and clamping said mold within said clamp; a computerized control system having an object-oriented program for controlling the operation of said clamp and translation of said screw during the molding cycle, said program including i) a clamp class corresponding to said clamp mechanism which, when instantiated, produces a composite clamp object effective to control said clamp and ii) a screw injector class corresponding to said screw injector mechanism which, when instantiated, produces a composite injector object effective to control the injection performed by said screw.