Digital computers have been used more and more to control different industrial processes during the last decade. As of today, many sy­ stems are designed to include a process control computer as a vital part. The use of computers has created a need for sophisticated me­ thods for the operation and supervision of complex industrial proces­ ses. To summarize the state of the art from the practical as well as from the theoretical point of view, the 4th IFACIIFIP International Conference on "Digital Computer Applications to Process Control" will be held at Zurich from March 19 to 22, 1974. The first two vo­ lumes of the proceedings contain the accepted papers submitted to the conference mentioned above. The papers are arranged according to the topics of the conference. A third volume will include the six follow­ ing survey papers: 1. Digital Control Algorithms Prof. A. P. Sage, Dallas Texas I USA 2. Interface Problems for Process Control Prof. T. J. Williams, Lafayette Indiana I USA 3. Software for Process Computers Dr. J. Gertler, Budapest I Hungary Dr. J. Sedlak, Prague I CSSR 4. Digital Computer Applications in Metallurgical Processes Mr. W. E. Miller, Salem I USA Mr. W. G. Wright, Schenectady I USA 5. Digital Computer Applications in Power Systems Mr. D. Ernst, Erlangen / FRG 6. Digital Computer Applications in Chemical and Oil Industries Dr. H.