DOEACC Society 2006 DOEACC C Level C3 Operating Systems ( ) - Question Paper

C3-R3: OPERATING SYSTEMS
NOTE:
Time: three Hours Total Marks: 100
1. ans the subsequent ques..
a) Briefly define the 4 major resource managers in a typical operating system.
b) explain why we have various processor modes and how these modes are used in
typical operating systems.
c) define the similarities and difference ranging from 2 various threads running in the
identical process and 2 independent processes.
d) What is the difference ranging from a physical address and a virtual address?
e) How can a CPU be brought from user mode to kernel mode? How it can be brought
back from the kernel mode to user mode? Justify your ans.
f) In what circumstances are interrupts more efficient than polling?
g) What is the difference ranging from multiprocessing and multiprogramming?
(7x4)
2. As a system administrator you have noticed that usage peaks ranging from 10:00 AM to 5:00
PM and ranging from 7:00 PM to 10:00 PM. The company's CEO decided to call on you to
design a system where during these peak hours there will be 3 levels of users. Users
in level one are to enjoy better response time than users in level 2, who in turn will enjoy
better response time than users in level 3. You are to design such a system so that all
users will still get a few progress, but with the indicated preferences in place.
a) Will a fixed priority scheme with pre-emption and three fixed priorities work? Why, or why
not?
b) Will a UNIX-style multi-feedback queue work? Why, or why not?
c) If none of the above works, could you design a scheduling scheme that meets the
requirements?
(5+5+8)
3.
a) Identify and discuss 3 styles of switching from user mode to supervisor mode.
b) A hardware designer argues that he has enough transistors on the chip to give 1024
integer registers and 512 floating point registers. You have been invited as the operating
system guru to provide opinion about the new design.
i) What is the effect of having such a large number of registers on the operating
system?
ii) What additional hardware features you would recommend added to the design
above.
(6+12)
C3-R3 Page one of two July, 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.
4.
a) Most round-robin schedulers use a fixed size quantum. provide an argument in favor of and
against a small quantum.
b) Consider a uniprocessor kernel that user programs can trap into using system calls. The
kernel receives and handles interrupt requests from I/O devices. Would there be any
need for critical parts within that kernel?
c) How 1 can prevent deadlock to take place in an operating system? discuss.
(6+6+6)
5.
a) describe critical part issue for process synchronization. discuss why it is difficult to
implement critical part issue.
b) Consider the subsequent program fragment:
P (s1);
a++;
P (s2);
v++;
V (s2);
V (s1);
(s1, s2 are semaphores). All variables are automatic. Now, consider 2 threads running
this fragment of code simultaneously, can there be a deadlock? Why, or why not.
(9+9)
6.
a) A minicomputer uses the buddy system for memory management. Initially it has one
block of 256K at address 0. After successive requests of 7K, 26K, 34K and 19K come in,
how many blocks are left and elaborate their sizes and addresses?
b) discuss working of virtual memory.
c) A computer whose processes have 512 pages in their address space keeps its page
tables in memory. The overhead needed for studying a word from the page table is 50
nsec. To decrease this overhead, the computer has a TLB that holds 32 entries and can do
lookups in 5nsec. What hit rate is needed to decrease the mean overhead to 20nsec?
(6+6+6)
7.
a) discuss salient features of I/O system of a general-purpose operating system.
b) Contiguous allocation of files leads to disk fragmentation. Is this internal or external
fragmentation?
c) Can we implement symbolic links in DOS (FAT file system)? If so, show how, and if not,
discuss why.
(12+3+3)
C3-R3 Page two of two July, 2006

Earning:   Approval pending.