Category: Operating System Objective Questions

Operating System Multiple Choice Questions on “Distributed Operating System”.

1. In distributed system, each processor has its own ___________
a) local memory
b) clock
c) both local memory and clock
d) none of the mentioned

Answer: c
Clarification: None.

2. If one site fails in distributed system then ___________
a) the remaining sites can continue operating
b) all the sites will stop working
c) directly connected sites will stop working
d) none of the mentioned

Answer: a
Clarification: None.

3. Network operating system runs on ___________
a) server
b) every system in the network
c) both server and every system in the network
d) none of the mentioned

Answer: a
Clarification: None.

4. Which technique is based on compile-time program transformation for accessing remote data in a distributed-memory parallel system?
a) cache coherence scheme
b) computation migration
c) remote procedure call
d) message passing

Answer: b
Clarification: None.

5. Logical extension of computation migration is ___________
a) process migration
b) system migration
c) thread migration
d) data migration

Answer: a
Clarification: None.

6. Processes on the remote systems are identified by ___________
a) host ID
b) host name and identifier
c) identifier
d) process ID

Answer: b
Clarification: None.

7. Which routing technique is used in a distributed system?
a) fixed routing
b) virtual routing
c) dynamic routing
d) all of the mentioned

Answer: d
Clarification: None.

8. In distributed systems, link and site failure is detected by ___________
a) polling
b) handshaking
c) token passing
d) none of the mentioned

Answer: b
Clarification: None.

9. The capability of a system to adapt the increased service load is called ___________
a) scalability
b) tolerance
c) capacity
d) none of the mentioned

Answer: a
Clarification: None.

10. Internet provides _______ for remote login.
a) telnet
b) http
c) ftp
d) rpc

Answer: a
Clarification: None.

Operating System Interview Questions and Answers for freshers on “Semaphores” and will also be useful for interview preparations for freshers.

1. What will happen if a non-recursive mutex is locked more than once?
a) Starvation
b) Deadlock
c) Aging
d) Signaling

Answer: b
Clarification: 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.

2. 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
Clarification: None.

3. What are the two kinds of semaphores?
a) mutex & counting
b) binary & counting
c) counting & decimal
d) decimal & binary

Answer: b
Clarification: None.

4. 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
Clarification: None.

5. 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
Clarification: 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.

6. A binary semaphore is a semaphore with integer values ____________
a) 1
b) -1
c) 0.8
d) 0.5

Answer: a
Clarification: None.

7. 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
Clarification: 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.

8. 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
Clarification: 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.

9. Semaphores are mostly used to implement ____________
a) System calls
b) IPC mechanisms
c) System protection
d) None of the mentioned

Answer: b
Clarification: None.

10. Spinlocks are intended to provide __________ only.
a) Mutual Exclusion
b) Bounded Waiting
c) Aging
d) Progress

Answer: b

Operating System MCQs on “Memory Management – Segmentation”

1. In segmentation, each address is specified by ____________
a) a segment number & offset
b) an offset & value
c) a value & segment number
d) a key & value

Answer: a
Clarification: None.

2. In paging the user provides only ________ which is partitioned by the hardware into ________ and ______
a) one address, page number, offset
b) one offset, page number, address
c) page number, offset, address
d) none of the mentioned

Answer: a
Clarification: None.

3. Each entry in a segment table has a ____________
a) segment base
b) segment peak
c) segment value
d) none of the mentioned

Answer: a
Clarification: None.

4. The segment base contains the ____________
a) starting logical address of the process
b) starting physical address of the segment in memory
c) segment length
d) none of the mentioned

Answer: b
Clarification: None.

5. The segment limit contains the ____________
a) starting logical address of the process
b) starting physical address of the segment in memory
c) segment length
d) none of the mentioned

Answer: c
Clarification: None.

6. The offset ‘d’ of the logical address must be ____________
a) greater than segment limit
b) between 0 and segment limit
c) between 0 and the segment number
d) greater than the segment number

Answer: b
Clarification: None.

7. If the offset is legal ____________
a) it is used as a physical memory address itself
b) it is subtracted from the segment base to produce the physical memory address
c) it is added to the segment base to produce the physical memory address
d) none of the mentioned

Answer: a
Clarification: None.

8. When the entries in the segment tables of two different processes point to the same physical location ____________
a) the segments are invalid
b) the processes get blocked
c) segments are shared
d) all of the mentioned

Answer: c
Clarification: None.

9. The protection bit is 0/1 based on ____________
a) write only
b) read only
c) read – write
d) none of the mentioned

Answer: c
Clarification: None.

10. If there are 32 segments, each of size 1Kb, then the logical address should have ____________
a) 13 bits
b) 14 bits
c) 15 bits
d) 16 bits

Answer: a
Clarification: To specify a particular segment, 5 bits are required. To select a particular byte after selecting a page, 10 more bits are required. Hence 15 bits are required.

11. Consider a computer with 8 Mbytes of main memory and a 128K cache. The cache block size is 4 K. It uses a direct mapping scheme for cache management. How many different main memory blocks can map onto a given physical cache block?
a) 2048
b) 256
c) 64
d) 8

Answer: c
Clarification: None.

12. A multilevel page table is preferred in comparison to a single level page table for translating virtual address to physical address because ____________
a) it reduces the memory access time to read or write a memory location
b) it helps to reduce the size of page table needed to implement the virtual address space of a process
c) it is required by the translation lookaside buffer
d) it helps to reduce the number of page faults in page replacement algorithms

Answer: b

Operating System Multiple Choice Questions on “Security – Program and System Threats”.

1. What is the breach of integrity?
a) This type of violation involves unauthorized reading of data
b) This violation involves unauthorized modification of data
c) This violation involves unauthorized destruction of data
d) This violation involves unauthorized use of resources

Answer: b
Clarification: None.

2. What is breach of confidentiality?
a) This type of violation involves unauthorized reading of data
b) This violation involves unauthorized modification of data
c) This violation involves unauthorized destruction of data
d) This violation involves unauthorized use of resources

Answer: a
Clarification: None.

3. What is theft of service?
a) This type of violation involves unauthorized reading of data
b) This violation involves unauthorized modification of data
c) This violation involves unauthorized destruction of data
d) This violation involves unauthorized use of resources

Answer: d
Clarification: None.

4. What is breach of availability?
a) This type of violation involves unauthorized reading of data
b) This violation involves unauthorized modification of data
c) This violation involves unauthorized destruction of data
d) This violation involves unauthorized use of resources

Answer: c
Clarification: None.

5. What is Trojan horse?
a) It is a useful way to encrypt password
b) It is a user which steals valuable information
c) It is a rogue program which tricks users
d) It’s a brute force attack algorithm

Answer: c
Clarification: None.

6. What is trap door?
a) IT is trap door in WarGames
b) It is a hole in software left by designer
c) It is a Trojan horse
d) It is a virus which traps and locks user terminal

Answer: b
Clarification: None.

7. Which mechanism is used by worm process?
a) Trap door
b) Fake process
c) Spawn Process
d) VAX process

Answer: c
Clarification: None.

8. Which of the following is not a characteristic of a virus?
a) Virus destroy and modify user data
b) Virus is a standalone program
c) Virus is a code embedded in a legitimate program
d) Virus cannot be detected

Answer: d
Clarification: Virus can be detected by having an antivirus program.

9. What is known as masquerading?
a) When one participant in communication pretends to be someone else
b) When attacker modifies data in communication
c) When attack is of fraudulent repeat of a valid data
d) When attack gains access to remote systems

Answer: a
Clarification: None.

10. Who unleashed famous worm attack in 1988 which effected UNIX systems and caused losses in millions?
a) Robert Morris
b) Bob Milano
c) Mark zuckerberg
d) Bill Gates

Answer: a
Clarification: None.

11. What is port scanning?
a) It is a software used to scan system for attack
b) It is a software application designed to probe a server or host for open ports
c) It is software used to scan system for introducing attacks by brute force
d) None of the mentioned

Answer: b
Clarification: None.

12. Which is not a port scan type?
a) TCP scanning
b) SYN scanning
c) UDP scanning
d) SYSTEM Scanning

Answer: d
Clarification: None.

13. Which is not a valid port scan type?
a) ACK scanning
b) Window scanning
c) IGMP scan
d) FIN scanning

Answer: c
Clarification: None.

14. What are zombie systems?
a) Are specific system which are designed to attack by manufacturer
b) They are network of known hacking group
c) These systems are previously compromised independent systems
d) None of the mentioned

Answer: c
Clarification: None.

15. What is known as a DOS attack?
a) It is attacked to block traffic of network
b) It is attacked to harm contents stored in HDD by worm spawn processes
c) It is an attempt to make a machine or network resource unavailable
d) None of the mentioned

Answer: c
Clarification: None.

16. With regard to DOS attack what is not true from below options?
a) We can stop DOS attack completely
b) By upgrading OS vulnerability we can stop DOS attack to some extent
c) DOS attack has to be stopped at network level
d) Such attack can last for hours

Answer: a

Operating System MCQs on “Virtual Memory – Page Replacement Algorithms”.

1. When using counters to implement LRU, we replace the page with the ____________
a) smallest time value
b) largest time value
c) greatest size
d) none of the mentioned

Answer: a
Clarification: Whenever a reference to a page is made, the contents of the clock register are copied into the time-of-use field in the page-table entry for that page. In this way, we always have the time of the last reference to each page.

2. In the stack implementation of the LRU algorithm, a stack can be maintained in a manner ____________
a) whenever a page is used, it is removed from the stack and put on bottom
b) the bottom of the stack is the LRU page
c) the top of the stack contains the LRU page and all new pages are added to the top
d) none of the mentioned

Answer: b
Clarification: None.

3. There is a set of page replacement algorithms that can never exhibit Belady’s Anomaly, called ____________
a) queue algorithms
b) stack algorithms
c) string algorithms
d) none of the mentioned

Answer: b
Clarification: None.

4. Applying the LRU page replacement to the following reference string.
1 2 4 5 2 1 2 4
The main memory can accommodate 3 pages and it already has pages 1 and 2. Page 1 came in before page 2.
How many page faults will occur?
a) 2
b) 3
c) 4
d) 5

Answer: c
Clarification: None.

5. Increasing the RAM of a computer typically improves performance because ____________
a) Virtual memory increases
b) Larger RAMs are faster
c) Fewer page faults occur
d) None of the mentioned

Answer: c
Clarification: None.

6. The essential content(s) in each entry of a page table is/are ____________
a) Virtual page number
b) Page frame number
c) Both virtual page number and page frame number
d) Access right information

Answer: b
Clarification: None.

7. The minimum number of page frames that must be allocated to a running process in a virtual memory environment is determined by ____________
a) the instruction set architecture
b) page size
c) physical memory size
d) number of processes in memory

Answer: a
Clarification: None.

8. What is the reason for using the LFU page replacement algorithm?
a) an actively used page should have a large reference count
b) a less used page has more chances to be used again
c) it is extremely efficient and optimal
d) all of the mentioned

Answer: a
Clarification: None.

9. What is the reason for using the MFU page replacement algorithm?
a) an actively used page should have a large reference count
b) a less used page has more chances to be used again
c) it is extremely efficient and optimal
d) all of the mentioned

Answer: b
Clarification: None.

10. The implementation of the LFU and the MFU algorithm is very uncommon because ____________
a) they are too complicated
b) they are optimal
c) they are expensive
d) all of the mentioned

Answer: c