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5K views55 pagesOS WB Madeeasy
Made easy operating system workbook
Uploaded by
gkushagra76Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF or read online on Scribd
/ 55
POSTAL
Study Course
2018
Computer Science & IT
Objective Practice Sets
fey chur eye)
Sl. Topic Page No.
4. Basic Concepts of OS 2
2, Process and Threads 4
3. CPUScheduling 7
4, Process Synchornization 2 18
5. Concurrency and Deadlock a
6. Memory Management 3%
7. Virtual Memory a
8. File System 50 |
9, Input-Output System 52
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Which of the following should be allowed only in
kernel mode?
1. Changing mapping from virtual to physical
address.
2. Mask and unmask interrupts
3, Disabling all intertups
4, Reading status of processor
5. Reading time of day
(@) 1,2and3 (b) 1,2,4and5
(©) 2,3and5 (d) allof these
An interrupt handler is a
(@) location in memory that keeps track of
recently generated interrupts
(©) peripheral device
(©) utility program
(d) special numeric code that indicates the
priority of a request
Executing more than one program concurrently
byone user on ene computer is known as
(@) muttiprogramming(o) time-sharing
(©) multitasking (d)__ multiprocessing
The simultaneous processing of two or more
programs by multiple processors is
(@) multitasking
(©) muttiprogramming
(©) time-sharing
(2) muttiprocessing
Which of the following does not interrupt a
running process?
(a) timer interrupts
(©) power failure
(b) device
(8) scheduling process
System call is used to access
(@) V0 functionality
(b) operating system functionality
Basic Concepts of OS
(6) application functionality
(6) None of the above
Q.7 Swapping is performed by
(@) longterm scheduler
(b) midterm scheduler
(©) short term scheduler
(@) dispatcher
Q.8 Choose the false statement
(a) static inking requires no support of OS
(b) dynamic linking requires no support of OS
(©) dynamic loading requires no support of OS
(@) none of the above
Q.9._ Assume that the kere! mode is non-preemptive
What happens when an I/O interrupt comes while
@ process 'P, is running in the kernel mode on
the CPU?
(@) CPUis given to the process for which the iY
Ohas completed
(0) CPUis given to some other process based
‘onthe scheduling policy
(©) P, continues to execute on the CPU
(d) None of the above
.10 Overlayis
(2) apartof an operating system
(0) a specitic memory location
(©) single contiguous memory that was used
inthe olden days for running large programs
by swapping
@) overloading the system with many user files
urs, an operating system
terrupt
198 the stage of the
88 atter processing the inte G3 MADE ERS!
(0) always resumes execution of the interrupted
process after processing the interrupt
(d) may change the state of the interrupted
process to “blocked! and schedule another
process
Q.12 Consider the following statements:
$1: The OSis designed tomaximize the resource
utilization.
$2: The control pragram manages the system
programs.
Which of the above statements is/are true?
(a) St is true $2 is false
(©) S2is true and St is false
() both $1 and $2 are true
(@) both $1 and $2 are false
PEEIIEEN 22s1c concepts of 05
1 @2 © 3 © 4 @ 5.
10. (@) 11. (@) 12 (@ 13. () 14,
Basic Concepts of OS
1. (a)
Only critical services must reside in the kernel
All services mentioned except reading status of
processors and reading time of the day are
crilical
Hence option (a) is correct,
9. (c)
‘When the kernel is non-preemptive and any
process's running ina kernel mode, then process
Continues torun until either it completes oritwalts
for some input/output.
1. @)
When a interrupt occurs operating system
decides the request on the fact thatthe interrupt
is higher priority or less priority. If less, the
rupted process is resumed and only after
in
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Operating System
0.13 Bootstrap loader is always stored in
(@) cache (©) ROM
(c) RAM (d) disk
Q.14 Which of the following is true?
(a) Overlays are used to increase the size of
physical memory.
(0) Overlays are used to increase the logical
address space,
(©) When overlays are used, the size of a
process is not limited to the size of physical
memory.
(d) Overlays are used whenever the physical
address space is smaller than the logical
address space.
(e)
the execution of process, the interruptis handle.
However if interrupt has higher priority the
processis blocked and interruptis entertainod
Hence an operating system may or may not
change the state of the interrupted process to
tblocked” and schedule another process.
14. (c)
By using the overlays we can execute much
greater processes simulianeously which cannot
bbe execute and reside inthe memory at the samo
time. In this the process to be executed process
brought to memory only when itis needed at the
time of execution.
Objective Prater Sts CorCia)
Which of the following statements comparing
the context of a thread with that of a process is
true?
(@) two processes will not share any context;
two threads ofa same process will only share
the data and the code (tex!) areas of the
context
(©) two processes will not share any context;
two threads of a same process will share
the data, code (text) and the stack areas of
the context
(©) two processes will share the data and the
code (tex!) areas of the user context; tivo
threads of a same process will only share
the register context
(d) the overhead invalved in context switching
for threads is much higher than that for
processes
Which of the following information is not part of
process control block
1, Process state 2, List of open files,
3. Processpagetable 4, Stack pointer
@ only3 (b) 3and4
(©) 2and4 (6) None of these
Convoy effect is a result of
(@) onelong CPU bound process and many other
CPU bound processes are waiting
(b) many CPU bound processes and less YO
bound processes
(6) many CPU and /O bound processes
(@) proper mix of CPU and /O bound processes
in a time-sharing operating system, when the
ime slot given to a process is completed, the
process goes from the RUNNING state to the
(@) BLOCKED state
(b) READY stat
(©) SUSPENDED state
(d) TERMINATED state
ota ated
Process and Threads
as
a6
a7
as
Inamuttiorogramming environment
(@) the processor executes more than one
process at atime
(b) the programs are developed by more than
one person
(©) more than one process resides in the memory
(@) asingle user can execute many programs
at the same time
It @ system contains n processors and n
processes then what will be maximum and
minimum processes in running state respectively.
@ an (b) 7,0
© m0 (0) Pn?
Match List-Iwith List-II select the correct answer
using the codes given below the lists:
List-1
A. run ready
B, run—>blocked
©. blocked > run
D. run—terminated
List-tl
1, notpossible
2. when a process terminates itself
3. when a process time quantum expires
4. when a process issues an input / output
request
Codes:
A B Cc D
@m 1 4 3 2
® 2 1 3 4
@ 3 4 1 2
@® 1 4 2 3
While designing a kernel, an operating system
designer must decide whether to support kemel-
levelor user-level threading, Which ofthe following
statements is/are true? G3 MBE EASY
1. Kemel-level threading may be preferable to
user-level threading because storing
information about user-level threads in the
process controlblock would create a security
risk
2. User-level threading may be preferable to
kernet-level treading because in user-ievel
threading, if one thread blacks on 1/0, the
process can continue.
(@) tonly (e)
(©) 1and2ony — (@)
2only
None of these
ag
Postal Study Course EOEE
Q.10
Consider the folowing statements with respect
to user-level threads and kernel-supported
threads
(Context switching is faster with kemnel- O17
supported threads
(i) For user-level threads, a system call can
block the entire process
(ii) Keme!-supported threads can be scheduled
independently
(iv) Userlevel threads are transparent to the
kernel
Which of the above statements are true?
(@) (ii, (it) and (is) only
(©) (i and Git) only
(©) (and (a) only
(©) (and (i) only
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Operating System |
Assume process A has 8 user level threads and
process B has 4 kernel-level threads. Consider
while process A is running in CPU, process B is
waiting in ready queue. If one of the thread in A
is blocked then find status of A threads and B
threads?
(@) AIA threads are blocked and all B threads
are blocked
AIA threads are blocked and B threads are
not blocked
(©) AIlB threads are blocked and A threads are
not blocked
None of these
(b)
@
Assume T, and T, are two threads of the same
process, Consider the folowing information
4. Datasection
2. Stack section
3. Code section
4, 1/0 files
Find which of the above information can be
shared by T, and T,,
@ 1.2.3 (o) 1.24
© 1.34 @) 2.34
Objective Practice Sets | Computer Science & IT
PEEIIIEN Process and threads
1 @ 2 @ 3 @ 4 © 5 ©)
10. (o) 11, ()
PEIEIE #rocess and threads
3. (a) 9.
CPU bound processes requires lat of processor
time, resulting in long wait for © bound
processes for the processor. This ettectis called
convey effect, It results in lower CPU and VO
devices utilization
6. (b)
men system contains ‘n' processor and ‘ni
processes, then maximum number of processes
in running state can be 'n’ with each processor
containing maximum of one process inthe running
state. The minimum number is zero with no
processor having a processin running state
hence correct option (b).
7. (c)
When a process issues an input/output request
then it goes from running state to blocked state.
When a process terminates itself it goes from
running state to terminate state.
A process cannot go to running state after
completing its 1/0, it most go to ready state.
Hence option (c) is correct
10.
11
Postal Study Course PLXE]}
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6. ) 7 © & @ % bb)
(b)
Kernel level threads can be scheduled
independently, For user level threads a system
cail can block the entire process and are not
transparent to kernel,
()
Process Ahas user-level threads. Whole process.
has single control block instead of maintaining
control block for each thread. So blocking one
thread cause all processes to block. Here
process A and process 6 are independent,
henceno relation between Aand 8,
+ Option (b) is correct.
(c)
Each thread needs a program counter and stack
section to keep the local variables of procedures.
‘So stack section can not be shared by threads.
option (0) iscorrect. Qt
a2
a3
as
3
CTT a
In round-robin scheduling there are ‘rn’ no. of
processes in ready queue and time slice is ‘q!
units in worst case, the interrupted process will
getthe CPU again after
(@) (n= 1)gunits —(b)_nqunits
(©) (q-1)nunits — ()_ (q+ 1)nunits
Consider 'n’ processes sharing the CPU in a
round-robin fashion. Assume that the context
switch takes “S seconds. What must be the
Quantum ‘q’ such that the overhead of context
switching is minimized and at the same time each
process is guaranteed to execute on the CPU
atleast once in every t seconds?
@) qs(t—nsy(n—1)
(©) qs(t~ns(a-1)
(©) qs (tryin + 1)
@) qsit-nsyn +1)
‘The process state transition diagram in the figure
isrepresentative of
a feinated) New.
a
(@) abatch operating system
(b) an operating system with a preemptive
scheduler
(€) an operating system with anon-preemotive
scheduier
(@) auni-programmed operating system
Consider the following set of processes that
arrive at time 0, with the length of the CPU-burst
time given in milliseconds:
Qs
as
CPU Scheduling
‘Whats the average waiting time in milliseconds
when we use the FCFS, and SJF scheduling
algorithms?
(@) 9.33, 4.33 (b) 50,433
© 50,26 (6) 26,26
A uniprocessor computer system only has two
processes, both of which alternate 10ms CPU
bursts with 90ms /0 bursts. Both the processes
wore created at neatly the same time, The /O of
both processes can proceed in parallel. Which
of the folowing scheduling strategies will result
in the least CPU utilization (over along period of
time) for this system?
(@) first come first serve scheduling
(b) shortest remaining time first scheduling
(©) static priority scheduling with different
priors for the two processes
(@) round robin scheduling with a time quantum
of Sms
Consider.the following set of processes that need
to be scheduled on a single CPU. All the times
are given in msec.
Process Name | Arrival Time | Burst Time
a ° 3
B 3 4
© 7 3
D 9 5
E 12 7
Which of the following will give minimum average.
waiting time for all five processes?
(@) FOFSoniy (b) RR(T.Q.=3) only
(©) SRIF only (6) Both (a) and (c) a7
as
ag
‘Computer Science & IT
Starvation can be avoided by which of the
following statements.
1. Byusing shortest job first resource allocation
policy.
2. By using first-come, first serve resource
allocation policy.
(@) J only
(©) 1 and 2 only
(©) 2only
(@) None ofthese
‘Suppose a system contains n processes and
system uses the round robin algorithm for CPU
scheduing then wnich data sttucture 's Gest
suited ready queue ofthe processes.
f@) stack (b) que
(c) circularqueue (d) ‘tree
If asystem contains CPU bound processes then
which of the following scheduling algorithm
produces maximum efficiency of he CPU.
(@) FIFO (0) round robin
(© SuF (@) priority
Q.10 The jobs are assumed to have arrived at time 0
an
and in the order p, 4, /. 8, t Caloulate the
Geparture time for job pit scheduling is round-
robin with time slice of 1
(@ 16 () 10
1 (@) 12
Below process arrive in the order P,, P,, P, and
are served in CFS order The average turn around
time is_and average waiting time is,
Process [CPU Burst time] Arrive time
Pi 5 0
Pe 3 1
By “a
Pe a
(2) 45miliseo, 6.25 milisec
(0) 85milisec, 4.75 milisec
(©) 8milisoc, 4.75 milisec
(4) 475 milisec, 8 milisec
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Q.12 Consider the following performance table for
FCFS scheduling. For this batch of processes,
the throughout will be
Postion | Jab arrival | Job completion
inbatch | time (ai | _ time (Ci)
7 3 3
2 8 10
3 10 6
4 | 2 8
5 15 2
(@) 0.184 (o) 0192
(c) 0.269 (@) 0.238
Q.13 Consider we have four processes P,, P,, P, and
and consider the following table, Consider the
a