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This paper discusses the design and implementation of an extension to IBM Operating System/360 that is called PCOS and is intended specifically for use in “real-time” control of IBM manufacturing processes and testing. The most important part of PCOS is a Real-Time Control Program (RTCP) which is initiated at system start-up time as a “never-ending” task. The RTCP controls the execution of application programs and permits system response to requests for their execution within a time on the order of 100 msec. Other contributions are an “express path” for handling input/output operations, an “interpartition communication” program that provides common core storage for use during the execution of application programs, and an appendage to the OS/360 supervisor program to serve a specially designed high-speed multiplexor called the “transmission control unit.”
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