Final exam
CS-330
Operating Systems and Networking
Fall 2003
Answer only one question from each of the Groups A and B
and two questions from Group C
No consultation (social or otherwise) in the class is permitted.
Time limit: Strictly two hours
Group A
1. What is the distinction between deadlock and starvation? Can a process be starved even if it gets
the CPU? Can deadlock involve only a subset of processes? Does a deadlocked process starve?
Explain all your answers.
2. Explain why it is difficult to implement a critical region.
3. A virtual address
a
in a paging system is equivalent to a pair (
d,p
), in which the first one
refers to the page number and the second one, the offset within the page. Let
z
be the number of
bytes in a page. Find algebraic relations that show
p
and
d
as functions of
z
and
w
.
Group B
4. Which provides the best average response time when there are multiple servers (bank tellers,
supermarket cashiers, airline check in stations, etc.): a single FIFO queue for all servers or a FIFO
queue per server? Why? Assume that you cannot predict how long any customer is going to take at
the server and that once a customer has picked a queue to wait in, they are stuck there and cannot
move to another queue.
5. A process has four frames allocated to it. The time of the last loading of each page into a frame,
the time of the last access to each page in the frame, the page number of each frame, the
referenced and the modified bits for each frame are as shown in the table below.
Page number Frame number Loading time Reference time R bit M bit
2 0 60 161 0 1
1 1 130 160 0 0
0 2 26 162 1 0
3 3 20 163 1 1
A page fault to page 4 has occurred. Which frame will have its content replaced for each of the
Following page replacement policies? Explain why in each case.
` a. FIFO
b. LRU
c. Clock
d. Optimal
e. Given the page reference string 4,0,0,0,2,4,2,1,0,3,2, how many page faults would
occur if a working set policy were used with a window of size 4? Show clearly when
page fault would occur.
6. Why is it expensive to switch between processes? Is it less expensive to switch between threads?
