The J. Stefan Institute in Ljubljana has developed a microcomputer-based multiloop controller MMC-90, which is, on the one hand, aimed at scientific research work, i.e. the study of the most modern techniques of control and, on the other hand, aimed at solving actual industrial problems. A program environment has been made, which allows design, simulation and automatic coding of control structures for this controller as well as other programmable microcomputer controllers (computer-aided control engineering method). The MMC-90 controller has already performed two interesting applications. The combustion control in a steam boiler PK-401 in Cinkarna Celje has been realised. Besides numerous other positive effects, 4% fuel has also been saved and ecological conditions have been greatly improved.