The control system of the OPAL detector at LEP

Abstract The OPAL detector at the LEP accelerator in CERN is an ensemble of 14 subdetectors provided by 24 institutions. A control system has been designed and implemented to ensure the safe operation of the detector and to present the operator with a coherent picture of the actual status of the whole experiment. All operational parameters are continuously monitored and automatic actions can be taken by the system. The hardware consists of about 30 VME stations, based on Motorola MC68020 microprocessors, running under the operating system OS-9. The software, written in FORTRAN and C, is organized in three layers: human interface, a suite of skeleton programs, and applications.