B.Sc. II (Semester III) (CBCS) Examination, 2018
COMPUTER SCIENCE (Paper III)
Operating System
Day and Date Monday, 3-12-2018 Max. Marks 70
Time 2.30 p.m. to 5.00 p.m.
N.B. All questions are compulsory.
Figures to the right indicate full marks.
1. Multiple choice questions. 14
In the blocked state
The process waiting for I/O is found
The process which is running is found
The process waiting for processor is found
All of the above
CPU can only execute programs which are stored in
Hard disk Floppy disk Job queue Ready queue
is not the state of the process.
Ready Privileged Running Blocked
Contiguous allocation with fixed partitions suffers from
fragmentation.
Internal External Both None
A process execution begins and ends with
I/O burst CPU burst Both None
is a synchronization tool.
Thread Semaphore Pipe Socket
The time taken by the disk arm to locate the specific address of a sector for
getting information is called
Rotational latency Search time
Seek time Response time
The execution of critical sections by the processes is
Progressive Mutually exclusive
Bounded waiting Relative speed
For deadlock detection used in single instance resource
type.
Wait-for graph Resource allocation graph
Variant graph Directed graph
10) Process attributes are stored in a
Stack Program control Block
Queue Process control block
11) Long term scheduler execute more frequently than short term scheduler.
True False
12) Demand paging is a virtual memory system.
True False
13) Equal priority processes are scheduled in SJF manner.
True False
14) In real time O.S., the response time is very critical
True False
2. Answer any four 8
Define Beladys Anamoly.
State the benefits of threads.
Define race condition.
What is disk access time
Define spinlock semaphore.
Answer any two 6
Define context switching with its drawback.
Differentiate between process and program.
Define fragmentation with its types.
3. Answer any two 8
Write a note on real time O.S.
State process scheduling criterias.
Define scheduler with its types.
Answer any one 6
Explain contiguous and linked file allocation methods.
Consider the following system scenario,
Allocation
A B C
J1 2 1 0
J2 3 2 3
J3 3 0 2
J4 3 2 0
J5 1 0 1
Solve by using Bankers algorithm and find out
Contents of need matrix.
ii) Is system is in safe state
iii) If J4 arrives with request 0 can be granted immediately.
4. Answer any two 10
Explain contiguous allocation with dynamic partition method.
Define O.S. with services provided by O.S.
Consider following system snapshot,
Jobs Arrival time CPU Burst Priority
J1 0 5 2
J2 2 4 1
J3 3 7 3
J4 5 6 4
Calculate average waiting time and average turn around time by using priority
scheduling algorithm and also draw Gantt chart.
Max.
A B C
J1 5 6 3
J2 8 5 6
J3 4 8 2
J4 7 4 3
J5 4 3 3
Available
A B C
3 3 2
Set P
Answer any one 4
Write note on producer-consumer problem.
If the disk head is located initially at 32, find the number of disk moves
required with FCFS, if the disk queue of I/O blocks requests are,
98, 37, 14, 124, 65, 67.
5. Answer any two 14
Explain concept of paging with diagram.
Explain PCB with diagram.
Calculate the number of page faults for the following reference string using,
FIFO page replacement algorithm
LRU page replacement algorithm
Optimal page replacement algorithm.
Frame size 3
Reference string
4 3 2 1 4 3 5 4 3 2 15