DOEACC Society 2006 DOEACC C Level Operating Systems ( ) - Question Paper

C3-R3: OPERATING SYSTEMS
NOTE:
Time: three Hours Total Marks: 100
1.
a) Does a process incur more execution overhead compared to a thread? Justify your
answer.
b) Distinguish ranging from multiprocessing and multiprogramming.
c) elaborate the “special files” in Unix?
d) What is the main difference ranging from worm and virus?
e) State the practical limitations of implementing non-preemptive SJF algorithm.
f) What is the difference ranging from a long-term scheduler and a short-term scheduler?
g) How can a single copy of a text editor be used to serve multiple users in a time-sharing
system?
(7x4)
2.
a) What is TLB? obtain out the effective memory-access time with an 80% hit ratio and the
subsequent access times:
TLB access time: 20ns; MM access time: 100ns
b) define the public-key encryption scheme and mention how is it advantageous to the
data-encryption standard.
(8+10)
3. Consider the subsequent page reference during a provided time interval for a memory
consisting of five frames: y,c,z,c,d,a,y,a,e,a,y,f,d,e. Using the i) FIFO replacement strategy
and ii) the LRU replacement strategy compare the outcomes. Repeat both FIFO and LRU
replacement strategies for memory with three frames and identical page reference trend.
Comment on the findings and draw a conclusion justifying the adoption of a particular
replacement strategy.
(18)
4.
a) What does ‘init’ do? What happens to the parent process id of a child when the parent
terminates before its child? When does a child become ‘zombie’?
b) With reference to Unix when do the subsequent situations occur?
i) Single process table entry contains pointers to the identical file table entry.
ii) various file table entries point to the identical i-node table entry.
iii) Shell ‘forks’ a copy of itself and ‘waits’ for the child to terminate.
c) How does CPU time-slice affect the Round-Robin algorithm?
(8+6+4)
5.
a) Show and discuss an implementation of the classical producer-consumer (producer
produces an item, keeps it in a buffer from where the consumer is picking it up) issue
using semaphore.
C3-R3 Page one of two January, 2006
1. ans ques. one and any 4 ques. from two to 7.
2. Parts of the identical ques. should be answered together and in the identical
sequence.
b) What is dynamic loading? Mention its advantage. How is dynamic linking performed?
Mention any disadvantage that you can think of for both the schemes.
(10+8)
6.
a) What is meant by a domain and the rights on it? define a Capability list and ways of
protecting it from user tampering.
b) Rewrite the subsequent code introducing code parallelism wherever applicable:
For i = one to k
a(i) = b(i) + c(i)
For j = one to k
d(j) = x(j) – y(j)
For p = one to k
x(p) = y(p) + b(p)
read(m,n,o,r)
q = m*n + r/o
write(q)
c) Using preemptive SJF(shortest-job-first) algorithm draw the Gannt chart and compute
the avg. waiting time for the subsequent processes:
Process Arrival time Burst time
P0 0 6
P1 two 4
P2 three 10
P3 seven 9
(9+4+5)
7.
a) Where and how “bit vector/table” is used? elaborate the advantages and disadvantages of
the technique?
b) What is deadlock? How can deadlock be prevented by not allowing “Hold and Wait” ? Is it a
feasible policy?
c) How can synchronization be achieved when 2 processes communicate by message
passing?
d) give a programming example of multithreading giving improved performance over a
single-threaded solution.
(5+5+5+3)
C3-R3 Page two of two January, 2006

Earning:   Approval pending.