CS439: Principles of Computer Systems
(Source: Alison Norman.)
Due: 8:45 AM Tuesday, January 22, 2013 Homeworks
will be submitted electronically. Please refer to the
homework turnin instructions.
Which of the following components is responsible for loading the
initial value in the program counter for an application program
before it starts running?
- Boot module or boot ROM
- From Anderson and Dahlin, Ch1 question 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.
- How should the operating system allocate 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 execute at the same
time, should it schedule the task with the least amount of work to do
or the most? Justify your answer.
You may assume a uniprocessor.
- How should the operating system allocate physical memory between
applications? What should happen if the set of applications does not
all fit in memory at the same time?
Note: These are thought questions---you are not expected to
determine how operating systems currently solve these problems.
Instead, you should think about how you would solve the problem.
- From Anderson and Dahlin, Ch1 question 2:
Now suppose the
computer system needs to support fault isolation. What hardware
and/or operating support do you think would be needed to protect an
application's data structure in memory from being corrupted by other
applications? Assume more than one application may reside in memory
at a time.
Again, a thought question.
- What differentiates a program, an
executable, and a process?
- Define three styles of switching from user mode to supervisor mode.
- Given the following piece of code:
main(int argc, char** argv)
void forkThem(int n)
How many processes are created if the above piece of code is run?
Inspect the manual for the system calls if you need more
information, but please solve the problem without compiling and
running the program. It may be easier to solve this problem by
System Calls vs. Procedure Calls:
How much more expensive is a system call than a procedure call? Write
a simple test program to compare the cost of a simple procedure call
to a simple system call ("getuid()" is a good candidate on
UNIX; see the man page.) (Note: be careful to prevent the optimizing
compiler from "optimizing out" your procedure calls. Do not
compile with optimization on.)
- Explain the difference (if any) between the time required by your
simple procedure call and simple system call by discussing what work
each call must do (be specific). [Note: Do not provide the source code
for your program, just the results].
Hint: You should use system calls such as gettimeofday()
for time measurements. Design your code such
that the measurement overhead is negligible. Also, be aware that timer
values in some systems have limited resolution (e.g., millisecond