Wang Laboratories, Inc.

A Edward Wild, Jr

An Wang

David Moros

Harold S Koplow

Donald R Dunning

A distributed data processing system having a magnetic disk and a master disk control and communication control unit; a slave work station unit having a keyboard for the input of data and a cathode ray tube display screen for the display of input data; and a slave output printer. The work station display is a CRT screen which can display 24 lines each of 80 characters, or a total of 1920 characters. The keyboard is similar to that of a standard electric typewriter with the addition of special instruction keys and keys for moving a cursor symbol on the screen. Optionally, other slave peripheral devices, such as a telecommunications link, a line printer, or a paper tape punch, may be provided. All slave units of the system are connected to the master unit by coaxial cables. Access to the disk for data reads and writes is under control of the master unit. Requests by slave devices for such access are signaled to the master unit by 'semaphores', which are specific areas in slave memory that may contain particular values indicating requests for particular services. Such semaphores are set by the slave, and are periodically polled and read by the master. The requested services are provided by the master, after which the master resets the semaphore value to a quantity indicating that the requested service has been completed. In addition to disk access, slave devices may request services of other slaves; these requests are relayed by the master.

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Merrimac, MA, United States of America

A Edward Wild, Jr