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Show 73 A process is just an instance of execution of a process description; there may be more than one process in existence at one time for a given process description. Parallel processes are required for operation of the system. The I/O, the display, the keyboard, the compiler, etc.,.must be able to run concurrently with the user^s .programs and with themselves. Moreover, the compiler. ',■ which is interacting with the user at the keyboard may' have to cun in parallel wich a logical "copy" of itself executing the com operator in a user program. Since this mechanism is needed it is no trick to allow the user in FLEX to create concurrent processes of his own-'-ail handled by the same algorithms. This ability is literally invaluable for all kinds of prograirmung, recursion, and event-oriented simulation- a pnrtfe use for the MM-8 00 0. Process Creation The basic idea is simple. Since the process description (the code} does not modify itself, it can contain no data. Therefore, it must have some way of accessing data which is independent of itself. Ir-process description reentry point A reentry point B |
