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system model

_ Finite number of resources in the system to be distributed among a number of competing processes

_ Partition the resources into several classes

_ Identical resources assigned to the same class (CPU cycles, memory space, _les, tape drives, printers)

_ Allocation of any instance of resource from a class will satisfy the request

_ State of the OS { allocation status of various resources

_ Process actions

·        request a resource

_ request a device

_ open a file

_ allocate memory

·        acquire/use a resource

_ read from/write to a device

_ read/write a _le

_ use the memory

·        release a resource

_ release a device

_ close a file

_ free memory

_ Resources acquired and used only through system calls

_ Allocation record to be maintained as a system table

_ State of the os changed only by the process actions

_ Processes to be modeled as nondeterministic entities

_ Deadlock when every process is waiting for an event that can be caused by only one of the waiting processes

_ Process pi { a partial function from system states into nonempty subsets of system states