The Common Process Model (CPM) subsystem provides a process model (shared memory threads) for VA Smalltalk. Standard operations include process creation and destruction, as well as process scheduling operations including suspend, resume, and change priority. Simple synchronization mechanisms are provided by semaphores. CPM is essentially an implementation of the process model described in the Blue Book (where you can find more details). Note that CPM does not include the Blue Book class SharedQueue.

Please refer to "The user interface process model" (in this book) for a discussion of the input event processing model on which the Common Widgets user interface is based.

CPM supports the running of multiple independent processes using four classes named Process, ProcessorScheduler, Delay, and Semaphore. An instance of Process represents a sequence of message sends that has an independent thread of execution. A unique instance of the class ProcessorScheduler, the global variable Processor, is responsible for scheduling these processes for execution by the virtual machine. Instances of Semaphore class provide a mechanism for process synchronization and (indirectly) communication. The class Delay enables processes to synchronize with the real-time clock and to control their execution with fixed time delays.