Anna University Chennai 2005 B.E Computer Science OPERATING SYSTEMS - Question Paper

Code: C-13 Subject: OPERATING SYSTEMS
Time: three Hours Max. Marks: 100
NOTE: There are 11 ques. in all.
ques. one is compulsory and carries 16 marks.
ans any 3 ques. every from Part I and Part II. every of these ques. carries 14 marks.
Any needed data not explicitly given, may be suitably presumed and said
Q.1 Answer the following: (2x8)

a.
On a system using round robin scheduling, let s represent the time needed to perform a process switch, q represent the round robin time quantum and r represent the avg. time a process runs before getting blocked for I/O. provide a formula for CPU efficiency provided that q > r.

b. On a system using round robin scheduling, what would be the effect of including 1 process twice in the list of processes?

c. On a system with 224 bytes of memory and fixed partitions, all of size 65,536 bytes, how many bits must the limit register have?

d. Why are page sizes always a power of 2?

e. On a simple paging system with a page table containing 64 entries of 11 bits (including valid / invalid bit) every and a page size of 512 bytes, how many bits are in a logical address?

f. A program has just learn the 1st record in a sequential access file. It next wants to learn the 10th record. How many records must the program learn to input the tenth?

g. On a system using fixed blocking with 20 byte records and 50 byte blocks, how much space will be wasted in every block?

h. Which RAID levels are useful in cases of failure of a single disk?
PART I
ans any 3 ques.. every ques. carries 14 marks.
Q.2 Define the subsequent terms :
(i) Virtual memory. (ii) Semaphores.
(iii) Process Control Block. (iv) Thread.
(v) Physical address. (vi) Multiprogramming.
(vii) situation Switching. (7 x two = 14)
Q.3 Differentiate ranging from the subsequent :
(i) Batch systems and time sharing systems.
(ii) Multiprogramming and multiprocessing.
(iii) Parallel and distributed systems.
(iv) Paging and segmentation. (3 ½ x four = 14)

Q.4 a. What do you understand by a critical section? State and discuss the important requirements that must be satisfied by a solution to the critical part issue. (8)

b. Show how the Test And Set solution guarantees mutual exclusion. (6)

Q.5 Discuss the subsequent scheduling algorithms :
(i) round robin.
(ii) 1st come 1st serve.
(iii) shortest remaining time.
(iv) shortest job first. (3 ½ x four = 14)

Q.6 a. Describe simple relocatable partition, multiple fixed partition and variable partitioned memory management schemes. (10)

b. What is a page fault? elaborate different steps to handle a page fault. (4)
PART II
ans any 3 ques.. every ques. carries 14 marks.
Q.7 a. On a system using simple segmentation, calculate the physical address for every of the logical addresses, provided the subsequent segment table. If the address generates a segment fault, indicate so. (5)
Segmet Base Length
0 330 124
1 876 211
2 111 99
3 498 302


(i) 0, 99 (ii) 2, 75
(iii) 1, 265 (iv) 3, 222
(v) 0, 111

b. Write down the banker's algorithm for deadlock avoidance. (5)

c. Describe the structure of the magnetic disk. (4)
Q.8 a. On a system using paging and segmentation, the virtual address space consists of up to eight segments where every segment can be up to 229 bytes long. The hardware pages every segment into 256 byte pages. How many bits in the virtual address specify the :
(i) Segment number. (ii) Page number.
(iii) Offset within page. (iv) Entire virtual address. (8)

b. Write down the main features of Unix Operating system. (6)

Q.9 a. Most operating systems improve performance by caching a few important file system data in main memory. Those operating systems require the computer to be shut down prior to turning the computer off. Why? (5)

b. What is an i-node? elaborate the trade-offs of using i-nodes? (4)

c. Differentiate ranging from physical dump and logical dump for dumping a disk to tape. (5)

Q.10 a. What are the advantages of using buffering for I/O operations. (2)

b. On a disk with 1000 cylinders, numbers 0 to 999, compute the number of tracks the disk arm must move to satisfy all the requests in the disk queue. presume the last request serviced was at track 360 and the head is moving towards track 0. The queue in fifo order contains requests for the subsequent tracks: 123, 870, 690, 478, 105, 376. perform the computations for the subsequent scheduling algorithms.

(i) SSTF.
(ii) SCAN.
(iii) FIFO. (12)

Q.11 Write short notes on the subsequent :

(i) Disk reliability.
(ii) Free space management.
(iii) Remote file access.
(iv) Real time scheduling. (3.5 x four = 14)

Earning:   Approval pending.