R09 - December, 2011 - Regular Examinations - Set - 4.

B. Tech III Year I Semester Examinations, December-2011
OPERATING SYSTEMS
(COMMON TO CSE, IT)
Time: 3 hours Max. Marks: 75
Answer any five questions
All questions carry equal marks
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1.a) In a multi programming and time –sharing environment, several users share the system simultaneously, This situation can result in various security problem:
i) What are two such problem?
ii) Can be ensure the same degree of security in a time-shared machine as in a dedicated machine? Explain your answer
b) Explain with a neat example how system calls used. [7 8]
2.a) State and explain the various states that a process can be in.
b) Consider the following set of process assumed to have arrived at time 0,
in the order P1,P2,P3,P4,P5 with the length of the CPU burst given in
milliseconds.(Assume low numbers for high priority)
Process Burst time Priority
P1 10 3
P2 1 1
P3 2 4
P4 1 5
P5 5 2
i) Using priority scheduling schedule there processes according to a Gantt chart
ii) Find the average waiting time (Assume low numbers for high priority). [7 8]
3.a) What are the three requirements that a solution to the critical section problem must satisfy?
b) Describe briefly a classic software –based solution and a hardware based solution to the critical –section problem. [7 8]
4.a) What is demand paging?
b) consider the following reference string 7,0,1,2,0,3,0,4,2,3,0,3,2,1,2,0,1,7,0,1.
Assume there are three frames. Apply LRU replacement algorithm to the reference sting above and find out how many page fonts are produced. Illustrate the LRU page replacement algorithm in detail and also two feasible implementation of the LRU algorithm. [7 8]
5.a) State and explain the conditions that characterize a deadlock.
b) Enumerate the methods for handling a deadlock
c) Explain deadlock recovery methods. [15]
6.a) Write short notes on
i) File sharing ii) Protection
b) Explain the indexed allocation method with neat diagram. [7 8]

7.a) Explain the following disk scheduling algorithm with proper diagram
i) FCFS
ii)ISSTF
iii) SCAN
iv) LOOK
b) State and explain the various procedures that the kerned I/O sub-system supervises.
8.a) Explain the following :
i) implementation of access maturity
ii) Revocation of access rights
b) Explain cryptography as a security tool. [7 8]
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