[en] Two minicomputers are used to perform real time monitoring of radioactive waste storage tanks on the Hanford Nuclear Reservation. The Computer Automated Surveillance System, CASS, consists of a network of six field microprocessors, a central microprocessor and two central Eclipse minicomputers. The field microprocessors are each responsible for monitoring alarm sensors, liquid levels and temperatures. The field microprocessors report alarm conditions immediately to the central microprocessor. The central minicomputer reports all alarm conditions to the user terminals, requests data from the field on a scheduled and requested basis, and generates reports. It handles all requests for information from the user and stores all incoming data for historical purposes. The CASS software consists of five major segments: (1) process creation, (2) report generation, (3) file updating, (4) terminal communication, and (5) microprocessor communication. Since CASS must operate 24 hours a day, 7 days a week, the system cannot be allowed to abnormally terminate. For this reason all processes are started by the creation process. Having a single process responsible for creating all other processes provides the ability to detect a failure of a subordinate process and to automatically restart the failed process. The report generation process schedules reports, requests the data to be gathered to produce the reports, forms the reports, and distributes the reports to the user terminals. The file updating process handles all data file modifications. There is a terminal communication process for each user terminal which is responsible for printing scheduled reports and for allowing the user to request information from the CASS system. The microprocessor communication process handles all communication with the central microprocessor