1. Concurrent access to shared data may result in ____________
a) data consistency
b) data insecurity
c) data inconsistency
d) none of the mentioned
Answer: c
Explanation: None.
2. A situation where several processes access and manipulate the same data concurrently and the outcome of the execution depends on the particular order in which access takes place is called ____________
a) data consistency
b) race condition
c) aging
d) starvation
Answer: b
Explanation: None.
3. The segment of code in which the process may change common variables, update tables, write into files is known as ____________
a) program
b) critical section
c) non – critical section
d) synchronizing
Answer: b
Explanation: None.
4. Which of the following conditions must be satisfied to solve the critical section problem?
a) Mutual Exclusion
b) Progress
c) Bounded Waiting
d) All of the mentioned
Answer: d
Explanation: None.
5. Mutual exclusion implies that ____________
a) if a process is executing in its critical section, then no other process must be executing in their critical sections
b) if a process is executing in its critical section, then other processes must be executing in their critical sections
c) if a process is executing in its critical section, then all the resources of the system must be blocked until it finishes execution
d) none of the mentioned
Answer: a
Explanation: None.
6. Bounded waiting implies that there exists a bound on the number of times a process is allowed to enter its critical section ____________
a) after a process has made a request to enter its critical section and before the request is granted
b) when another process is in its critical section
c) before a process has made a request to enter its critical section
d) none of the mentioned
Answer: a
Explanation: None.
7. A minimum of _____ variable(s) is/are required to be shared between processes to solve the critical section problem.
a) one
b) two
c) three
d) four
Answer: b
Explanation: None.
8. In the bakery algorithm to solve the critical section problem ____________
a) each process is put into a queue and picked up in an ordered manner
b) each process receives a number (may or may not be unique) and the one with the lowest number is served next
c) each process gets a unique number and the one with the highest number is served next
d) each process gets a unique number and the one with the lowest number is served next
Answer: b
Explanation: None.
9. An un-interruptible unit is known as ____________
a) single
b) atomic
c) static
d) none of the mentioned
Answer: b
Explanation: None.
10. TestAndSet instruction is executed ____________
a) after a particular process
b) periodically
c) atomically
d) none of the mentioned
Answer: c
Explanation: None.
11. Semaphore is a/an _______ to solve the critical section problem.
a) hardware for a system
b) special program for a system
c) integer variable
d) none of the mentioned
Answer: c
Explanation: None.
12. What are the two atomic operations permissible on semaphores?
a) wait
b) stop
c) hold
d) none of the mentioned
Answer: a
Explanation: None.
13. What are Spinlocks?
a) CPU cycles wasting locks over critical sections of programs
b) Locks that avoid time wastage in context switches
c) Locks that work better on multiprocessor systems
d) All of the mentioned
Answer: d
Explanation: None.
14. What is the main disadvantage of spinlocks?
a) they are not sufficient for many process
b) they require busy waiting
c) they are unreliable sometimes
d) they are too complex for programmers
Answer: b
Explanation: None.
15. The wait operation of the semaphore basically works on the basic _______ system call.
a) stop()
b) block()
c) hold()
d) wait()
Answer: b
Explanation: None.
16. The signal operation of the semaphore basically works on the basic _______ system call.
a) continue()
b) wakeup()
c) getup()
d) start()
Answer: b
Explanation: None.
17. If the semaphore value is negative ____________
a) its magnitude is the number of processes waiting on that semaphore
b) it is invalid
c) no operation can be further performed on it until the signal operation is performed on it
d) none of the mentioned
Answer: a
Explanation: None.
18. The code that changes the value of the semaphore is ____________
a) remainder section code
b) non – critical section code
c) critical section code
d) none of the mentioned
Answer: c
Explanation: None.
19. The following program consists of 3 concurrent processes and 3 binary semaphores. The semaphores are initialized as S0 = 1, S1 = 0, S2 = 0.
Process P0
while(true)
{
wait(S0);
print '0';
release(S1);
release(S2);
}
Process P1
wait(S1);
release(S0);
Process P2
wait(S2);
release(S0);How many times will P0 print ‘0’?
a) At least twice
b) Exactly twice
c) Exactly thrice
d) Exactly once
Answer: a
Explanation: None.
20. Each process Pi, i = 0,1,2,3,……,9 is coded as follows.
repeat
P(mutex)
{Critical Section}
V(mutex)
foreverThe code for P10 is identical except that it uses V(mutex) instead of P(mutex). What is the largest number of processes that can be inside the critical section at any moment (the mutex being initialized to 1)?
a) 1
b) 2
c) 3
d) None of the mentioned
Answer: c
Explanation: Any one of the 9 processes can get into critical section after executing P(mutex) which decrements the mutex value to 0. At this time P10 can enter critical section by incrementing the value to 1. Now any of the 9 processes can enter the critical section by again decrementing the mutex value to 0. None of the remaining processes can get into their critical sections.
21. Two processes, P1 and P2, need to access a critical section of code. Consider the following synchronization construct used by the processes.
Process P1 :
while(true)
{
w1 = true;
while(w2 == true);
Critical section
w1 = false;
}
Remainder Section
Process P2 :
while(true)
{
w2 = true;
while(w1 == true);
Critical section
w2 = false;
}
Remainder SectionHere, w1 and w2 have shared variables, which are initialized to false. Which one of the following statements is TRUE about the above construct?
a) It does not ensure mutual exclusion
b) It does not ensure bounded waiting
c) It requires that processes enter the critical section in strict alternation
d) It does not prevent deadlocks but ensures mutual exclusion
Answer: d
Explanation: None.
22. What will happen if a non-recursive mutex is locked more than once?
a) Starvation
b) Deadlock
c) Aging
d) Signaling
Answer: b
Explanation: If a thread which had already locked a mutex, tries to lock the mutex again, it will enter into the waiting list of that mutex, which results in a deadlock. It is because no other thread can unlock the mutex.
23. What is a semaphore?
a) is a binary mutex
b) must be accessed from only one process
c) can be accessed from multiple processes
d) none of the mentioned
Answer: c
Explanation: None.
24. What are the two kinds of semaphores?
a) mutex & counting
b) binary & counting
c) counting & decimal
d) decimal & binary
Answer: b
Explanation: None.
25. What is a mutex?
a) is a binary mutex
b) must be accessed from only one process
c) can be accessed from multiple processes
d) none of the mentioned
Answer: b
Explanation: None.
26. At a particular time of computation the value of a counting semaphore is 7.Then 20 P operations and 15 V operations were completed on this semaphore. The resulting value of the semaphore is? (GATE 1987)
a) 42
b) 2
c) 7
d) 12
Answer: b
Explanation: P represents Wait and V represents Signal. P operation will decrease the value by 1 every time and V operation will increase the value by 1 every time
27. A binary semaphore is a semaphore with integer values ____________
a) 1
b) -1
c) 0.8
d) 0.5
Answer: a
Explanation: None.
28. The following pair of processes share a common variable X.
Process A
int Y; A1: Y = X*2; A2: X = Y; Process B int Z; B1: Z = X+1; B2: X = Z;
X is set to 5 before either process begins execution. As usual, statements within a process are executed sequentially, but statements in process A may execute in any order with respect to statements in process B.
How many different values of X are possible after both processes finish executing?
a) two
b) three
c) four
d) eight
Answer: c
Explanation: Here are the possible ways in which statements from A and B can be interleaved.
A1 A2 B1 B2: X = 11
A1 B1 A2 B2: X = 6
A1 B1 B2 A2: X = 10
B1 A1 B2 A2: X = 10
B1 A1 A2 B2: X = 6
B1 B2 A1 A2: X = 12.
29. The program follows to use a shared binary semaphore T.
Process A int Y; A1: Y = X*2; A2: X = Y; signal(T); Process B int Z; B1: wait(T); B2: Z = X+1; X = Z;
T is set to 0 before either process begins execution and, as before, X is set to 5.
Now, how many different values of X are possible after both processes finish executing?
a) one
b) two
c) three
d) four
Answer: a
Explanation: The semaphore T ensures that all the statements from A finish execution before B begins. So now there is only one way in which statements from A and B can be interleaved:
A1 A2 B1 B2: X = 11.
30. Semaphores are mostly used to implement ____________
a) System calls
b) IPC mechanisms
c) System protection
d) None of the mentioned
Answer: b
Explanation: None.
31. Spinlocks are intended to provide __________ only.
a) Mutual Exclusion
b) Bounded Waiting
c) Aging
d) Progress
Answer: b
Explanation: None.
32. The bounded buffer problem is also known as ____________
a) Readers – Writers problem
b) Dining – Philosophers problem
c) Producer – Consumer problem
d) None of the mentioned
Answer: c
Explanation: None.
33. In the bounded buffer problem, there are the empty and full semaphores that ____________
a) count the number of empty and full buffers
b) count the number of empty and full memory spaces
c) count the number of empty and full queues
d) none of the mentioned
Answer: a
Explanation: None.
34. In the bounded buffer problem ____________
a) there is only one buffer
b) there are n buffers ( n being greater than one but finite)
c) there are infinite buffers
d) the buffer size is bounded
Answer: b
Explanation: None.
35. To ensure difficulties do not arise in the readers – writers problem _______ are given exclusive access to the shared object.
a) readers
b) writers
c) readers and writers
d) none of the mentioned
Answer: b
Explanation: None.
36. The dining – philosophers problem will occur in case of ____________
a) 5 philosophers and 5 chopsticks
b) 4 philosophers and 5 chopsticks
c) 3 philosophers and 5 chopsticks
d) 6 philosophers and 5 chopsticks
Answer: a
Explanation: None.
37. A deadlock free solution to the dining philosophers problem ____________
a) necessarily eliminates the possibility of starvation
b) does not necessarily eliminate the possibility of starvation
c) eliminates any possibility of any kind of problem further
d) none of the mentioned
Answer: b
Explanation: None.
38. All processes share a semaphore variable mutex, initialized to 1. Each process must execute wait(mutex) before entering the critical section and signal(mutex) afterward.
Suppose a process executes in the following manner.
signal(mutex);
..... critical section ..... wait(mutex);
In this situation :
a) a deadlock will occur
b) processes will starve to enter critical section
c) several processes maybe executing in their critical section
d) all of the mentioned
Answer: c
Explanation: None.
39. All processes share a semaphore variable mutex, initialized to 1. Each process must execute wait(mutex) before entering the critical section and signal(mutex) afterward.
Suppose a process executes in the following manner.
wait(mutex); ..... critical section ..... wait(mutex);
a) a deadlock will occur
b) processes will starve to enter critical section
c) several processes maybe executing in their critical section
d) all of the mentioned
Answer: a
Explanation: None.
40. Consider the methods used by processes P1 and P2 for accessing their critical sections whenever needed, as given below. The initial values of shared boolean variables S1 and S2 are randomly assigned. (GATE 2010)
Method used by P1 :
while(S1==S2); Critical section S1 = S2; Method used by P2 : while(S1!=S2); Critical section S2 = not(S1);
Which of the following statements describes properties achieved?
a) Mutual exclusion but not progress
b) Progress but not mutual exclusion
c) Neither mutual exclusion nor progress
d) Both mutual exclusion and progress
Answer: d
Explanation: None.
41. A monitor is a type of ____________
a) semaphore
b) low level synchronization construct
c) high level synchronization construct
d) none of the mentioned
Answer: c
Explanation: None.
42. A monitor is characterized by ____________
a) a set of programmer defined operators
b) an identifier
c) the number of variables in it
d) all of the mentioned
Answer: a
Explanation: None.
43. A procedure defined within a ________ can access only those variables declared locally within the _______ and its formal parameters.
a) process, semaphore
b) process, monitor
c) semaphore, semaphore
d) monitor, monitor
Answer: d
Explanation: None.
44. The monitor construct ensures that ____________
a) only one process can be active at a time within the monitor
b) n number of processes can be active at a time within the monitor (n being greater than 1)
c) the queue has only one process in it at a time
d) all of the mentioned
Answer: a
Explanation: None.
45. What are the operations that can be invoked on a condition variable?
a) wait & signal
b) hold & wait
c) signal & hold
d) continue & signal
Answer: a
Explanation: None.
46. Which is the process of invoking the wait operation?
a) suspended until another process invokes the signal operation
b) waiting for another process to complete before it can itself call the signal operation
c) stopped until the next process in the queue finishes execution
d) none of the mentioned
Answer: a
Explanation: None.
47. If no process is suspended, the signal operation ____________
a) puts the system into a deadlock state
b) suspends some default process execution
c) nothing happens
d) the output is unpredictable
Answer: c
Explanation: None.
48. A collection of instructions that performs a single logical function is called ____________
a) transaction
b) operation
c) function
d) all of the mentioned
Answer: a
Explanation: None.
49. A terminated transaction that has completed its execution successfully is ____________ otherwise it is __________
a) committed, destroyed
b) aborted, destroyed
c) committed, aborted
d) none of the mentioned
Answer: c
Explanation: None.
50. The state of the data accessed by an aborted transaction must be restored to what it was just before the transaction started executing. This restoration is known as ________ of transaction.
a) safety
b) protection
c) roll – back
d) revert – back
Answer: c
Explanation: None.
51. Write ahead logging is a way ____________
a) to ensure atomicity
b) to keep data consistent
c) that records data on stable storage
d) all of the mentioned
Answer: d
Explanation: None.
52. In the write ahead logging a _____________ is maintained.
a) a memory
b) a system
c) a disk
d) a log record
Answer: d
Explanation: None.
53. An actual update is not allowed to a data item ____________
a) before the corresponding log record is written out to stable storage
b) after the corresponding log record is written out to stable storage
c) until the whole log record has been checked for inconsistencies
d) all of the mentioned
Answer: a
Explanation: None.
54. The undo and redo operations must be _________ to guarantee correct behaviour, even if a failure occurs during recovery process.
a) idempotent
b) easy
c) protected
d) all of the mentioned
Answer: a
Explanation: Idempotent – Multiple executions of an operation have the same result as does one execution.
55. The system periodically performs checkpoints that consists of the following operation(s) ____________
a) Putting all the log records currently in main memory onto stable storage
b) putting all modified data residing in main memory onto stable storage
c) putting a log record onto stable storage
d) all of the mentioned
Answer: d
Explanation: None.
56. Consider a transaction T1 that committed prior to checkpoint. The <T1 commits> record appears in the log before the <checkpoint> record. Any modifications made by T1 must have been written to the stable storage either with the checkpoint or prior to it. Thus at recovery time ____________
a) There is a need to perform an undo operation on T1
b) There is a need to perform a redo operation on T1
c) There is no need to perform an undo and redo operation on T1
d) All of the mentioned
Answer: c
Explanation: None.
57. Serializable schedules are ones where ____________
a) concurrent execution of transactions is equivalent to the transactions executed serially
b) the transactions can be carried out one after the other
c) a valid result occurs after execution transactions
d) none of the mentioned
Answer: a
Explanation: None.
58. A locking protocol is one that ____________
a) governs how locks are acquired
b) governs how locks are released
c) governs how locks are acquired and released
d) none of the mentioned
Answer: c
Explanation: None.
59. The two phase locking protocol consists of ____________
a) growing & shrinking phase
b) shrinking & creation phase
c) creation & growing phase
d) destruction & creation phase
Answer: a
Explanation: None.
60. The growing phase is a phase in which?
a) A transaction may obtain locks, but does not release any
b) A transaction may obtain locks, and releases a few or all of them
c) A transaction may release locks, but does not obtain any new locks
d) A transaction may release locks, and does obtain new locks
Answer: a
Explanation: None.
61. The shrinking phase is a phase in which?
a) A transaction may obtain locks, but does not release any
b) A transaction may obtain locks, and releases a few or all of them
c) A transaction may release locks, but does not obtain any new locks
d) A transaction may release locks, and does obtain new locks
Answer: c
Explanation: None.
62. Which of the following concurrency control protocols ensure both conflict serializability and freedom from deadlock?
I) 2-phase locking
II) Timestamp ordering
a) I only
b) II only
c) Both I and II
d) Neither I nor II
Answer: b
Explanation: None.
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