SRM University 2007 B.Tech Computer Science and Engineering BANK : OPERATING SYSTEMS - Question Paper

6.A process has four page frames allocated to it.The time of the last loading of the page frame, the time of the last access to the page in every page frame, the virtual page number in every frame, and the referenced ( R ) and replaced (M) bits for every frame are as shown( the times are clock ticks from the process begin at time 0 to the event).



Virtual page
Number Page Frame Time
loaded Time
referenced 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 virtual page four has occurred.Which page frame will have its contents changed for every of the subsequent memory management policies?Explain why in every case.
a)FIFO
b)LRU
c)Clock
d)Optimal

7.A process has four page frames allocated to it.The time of the last loading of the page frame, the time of the last access to the page in every page frame, the virtual page number in every frame, and the referenced ( R ) and replaced (M) bits for every frame are as shown( the times are clock ticks from the process begin at time 0 to the event).

Virtual page
Number Page Frame Time
loaded Time
referenced 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


provided the above state of memory, consider the subsequent virtual page reference string:

4,0,0,0,2,4,2,1,0,3,2

How many page faults would occur if the working set policy were used with a window size of four instead of a fixed allocation?Show clearly when every page fault would occur.


8.a)Explain how address translation is implemented in a 2 level paging system.
b)With the help of a flow chart, discuss the operation of paging and translation lookaside buffer.

9)a)Explain the principles of combined paging and segmentation scheme.
b)Consider a page reference string for a process with a working set of M frames, initially all empty.The page reference string is of length P with N distinct page numbers in it.For any page replacement algorithm,
i. What is a lower bound on the number of page faults?
ii. What is an upper bound on the number of page faults?

10.Consider a system with memory mapping done on a page basis and using single level page table.Assume that the necessary page table is always in memory.
a)If a memory reference takes 200ns, how long does a paged memory reference take?
b)Now , an MMU is added that imposes an overhead of 20ns on a hit or miss.If we presume that 85% of all memory references hit in the MMU TLB, what is the effective access time?
c)Explain how the TLB hit rate affects the EMAT?



V UNIT


PART A
1.What is block-oriented devices?
2.Explain DMA.
3.What is buffereing?
4.Compare data rates ranging from Floppy disks and hard drive.
5.What is buffer swapping?
6.Explain CSCAN method.
7.What is Nstep SCAN and FSCAN.
8.What is disk cache?
9.Explain file management system.
10.What is indexed sequential file?
11.What is hashed file?
12.Explain variable length blocking .
13.What is NTFS?
14.Explain indexed file allocation.
15.What is INODE?
16.What is the difference ranging from logical I/O and device I/O?
17.What is the importance of double buffer than single buffer.?
18.What delay elements are involved in disk read/write?
19.What is the typical disk sector size?
20.What criteria are important in choosing file organizations?
21.Why is the avg. search time to obtain a record in a file less for an indexed sequential file than for a sequential file?
22.List the 3 blocking methods.
23.List and briefly describe 3 file allocation methods.
24.What are typical access rights that may be granted or denied to a particular user for a particular file.?
25.What is the difference ranging from a file and database.
26.What is seek time?
27.What is rotational delay?
28.Explain stream oriented devices?
29.Explain double buffer and circular buffering?
30.Explain SSTF algorithm?
31.What is the difference ranging from FSCAN and CSCAN?
32.What is tape drive?
33.Explain device driver?
34.What is the difference ranging from indexed and indexed sequential file?
35.What is pile file method?
36. discuss why SSTF scheduling tends to favor middle cylinders over the innermost and
outermost cylinders.

PART B
1. Discuss the evolution of I/O functions.
2. Explain the subsequent I/O organizations model.
a.Local peripheral device.
b.Communications port.
c.File system.
3 discuss the different I/O buffer schemes?
4 What are the different disk scheduling polices? discuss.
5 Explain the design and performance considerations of disk cache.
6 a)Explain the basic file system architecture.
b) The disk rotates at 7,200 RPM,
i)What is the avg. rotational latency of this disk drive?
ii)What seek distance can be covered in the time that you obtained for part a?

7 Explain the different file organizations methods in detail with diagrams.
8 What are the different record blocking methods? discuss in detail.
9 What are the different file allocation methods ? discuss in detail?
10 Write notes on File directories.
11. Suppose that a disk drive has 5,000 cylinders, numbered 0 to 4999. The drive is currently
serving a request at cylinder 143, and the previous request was at cylinder 125. The queue of pending requests, in FIFO order, is
86,1470,913,1774,948,1509,1022,1750,130.
Starting from the current head position, what is the total distance (in cylinders) that the disk arm moves to satisfy all the pending requests for every of the subsequent disk-scheduling algorithms?
a.FCFS
b.SSTF
c.SCAN
d.LOCK
e.C-SCAN
f..C-LOOK

12.Compare the performance of C-SCAN and SCAN scheduling, assuming a uniform
distribution of requests. Consider the avg. response time (the time ranging from the arrival of
a request and the completion of the request’s service), the variation in response time, and the
effective bandwidth.How does performance depend on the relative sizes of seek time and
rotational latency?

Earning:   Approval pending.