A design system employing computer aided design techniques, a Gerber digital photographic plotter, and an automatic LSI tester has been developed and used in logic design, layout design, mask generation, and testing, of complex MOS Large Scale Integrated circuit arrays. The system employs computer logic simulation for debugging machine logic and generating test tapes, and utilizes abbreviated input data techniques for generating array layout designs and photographic artwork masters. In this system a major portion of the creative array design work is performed manually and detailed design and analysis is performed by the computer. In the design of the computer process, major emphasis was placed on detecting design errors and violations of design rules. As a result of this approach a very flexible computer aided design system has been developed which provides highly accurate custom MOS complex array designs in reasonably short turnaround-time with a minimum of design errors. The system is designed so that more automation features, that will perform additional creative design steps, may be incorporated as they are developed. Due to its modularity, modifications which will take advantage of advanced circuits, advanced fabrication processes, and second source vendors may be carried out at appropriate intervals with minimum system development and reprogramming.