A KNOWLEDGE-BASED OPERATION PLANNING SYSTEM, TURNPLAN, IS DESCRIBED. ITS MAIN FUNCTION INITIALLY CONSISTS OF DETERMINATION OF THE SEQUENCE OF OPERATIONS, CUTTING PARAMETERS, AND CUTTING TOOLS. TO MAKE THIS SYSTEM A COMPLETE WORKING MODULE FOR FULL INTEGRATION OF CAD/CAM, ITS KNOWLEDGE BASE HAS BEEN FURTHER UPGRADED SO THAT DETERMINATION OF WORKHOLDING METHODS, NC PART PROGRAMS GENERATION, AND TOOL PATH GENERATION ARE COMPRISED IN THE SYSTEM. THE SYSTEM IS DEVELOPED ON A PC-BASED COMPUTER USING PROLOG, WHICH IS FOUND SUITABLE FOR INDUSTRIAL APPLICATIONS. A PRACTICAL EXAMPLE HIGHLIGHTS CERTAIN FEATURES OF THE SYSTEM AND THE PAPER CONCLUDES WITH IMPLICATIONS FOR FURTHER RESEARCH.