In this course,
we shall distinguish between policy and mechanism.
Policies are ways to choose which activities to perform.
Mechanisms are the implementations that enforce policies,
and often depend to some extent on the hardware on which the
operating system runs.
For instance,
a processes may be granted resources using the first come, first serve policy.
This policy may be implemented using a queue of requests.
Often the kernel provides mechanisms that are used to implement policies
in servers.