Mid-sized, and later even small, companies bought their own computer capacity, thanks to an enormous improvement in the cost effectiveness of computer hardware. This was also true for companies that worked in small -sized and single-item production whose basis of existence was fulfillment of special customer requirements. These users discovered that the program packages available for planning & control had not been developed for their needs. Optimized manual solutions for operational organization in these companies turned out to be a treasure chest of ideas for innovation in the form of improved or even novel techniques in computer-aided planning & control.