Operating systems for such machines now incorporate all the features of large computer
operating systems of the past.
In fact, operating systems such as UNIX, originally developed to support terminals connected to a central
computer, have been moved to personal computer platforms. Microsoft??™s operating systems, on the other hand,
have grown from single-user-only environments to fully featured operating systems that even include multiuser
and multiprocessor support.
When computers on the network provide resources to other computers, such as a web server does, the
computers are called servers. Networked computers that access the services and data of other machines on the
network are called clients. Often a single computer may act as both client and server at different times.
MULTIPROCESSOR OPERATING SYSTEMS
Computers with multiple processors offer the potential of greater computational speed. With this potential
comes complexity, however. The complexity surrounds the shared resources that must be managed properly in
a multiprocessor environment.
For instance, there will be a Ready queue of processes to be run. Should there be a Ready queue of
programs to run for each CPU? Should instead each CPU inspect the same Ready queue that all share? Should
one CPU handle the scheduling for all the other CPUs? Or, should each CPU make its own scheduling
decisions? What about shared I/O devices and device tables? What about shared memory and the allocation of
processes to memory?
The simpler approach to a multiprocessor OS is to have one CPU be the ???master??? and have it make decisions
on behalf of the other ???slave??? CPUs.
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