The hardware and software structure of the control and data acquisition system (CODAS) of the Joint European Torus is described. CODAS is a large distributed real-time process control system. The operation is centralized in two adjacent control rooms through a fully programmable man-machine interface. The plant interface is based on CAM AC instrumentation and Eurocard signal conditioning. The system is based on a network of minicomputers with a link to a host mainframe.