Information Technology Reference
In-Depth Information
1. Suppose a computer system and all of its applications are completely bug
free. Suppose further that everyone in the world is completely honest and
trustworthy. In other words, we do not need to consider fault isolation.
a. How should the operating system allocate time on the processor?
Should it give all of the processor to each application until it no
longer needs it? If there are multiple tasks ready to go at the same
time, should it schedule the task with the least amount of work to
do or the one with the most? Justify your answer.
b. How should the operating system allocate physical memory between
applications? What should happen if the set of applications do not
all fit in memory at the same time?
c. How should the operating system allocate its disk space? Should the
first user to ask be able to grab all of the free space? What would
the likely outcome be for that policy?
2. Now suppose the computer system needs to support fault isolation. What
hardware and/or operating support do you think would be needed to ac-
complish this goal?
a. For protecting an application's data structures in memory from being
corrupted by other applications?
b. For protecting one user's disk les from being accessed or corrupted
by another user?
c. For protecting the network from a virus trying to use your computer
to send spam?
3. How should an operating system support communication between appli-
cations?
a. Through the file system?
b. Through messages passed between applications?
c. Through regions of memory shared between the applications?
d. All of the above? None of the above?
1.1.2
Mask hardware limitations: Operating system as il-
lusionist
A second important role of operating systems is to mask the restrictions inherent
in computer hardware. Hardware is necessarily limited by physical constraints
| a computer has only a limited number of processors and a limited amount
