Advance Operating System Quiz

1. Which of the following is the reason that the least recently used (LRU) algorithm is usually not used as a page replacement algorithm?

A. Other practical schemes such as MIN do a better job.

B. LRU requires knowledge of the future to work correctly.

C. LRU is too inefficient to implement in practice.

D. The Clock algorithm always outperforms LRU.

 

2. Which of the following are shared between threads in the same process?

A. registers

B. page table

C. stack

D. stack pointer

E. None of these are shared

 

3. The IP service model guarantees which of the following?

A. The contents of a packet will not be corrupted

B. That at least one copy of a packet will arrive at the destination

C. That no more than one copy of a packet will arrive at the destination

D. That packets sent in order will be delivered in order

E. None of the above

 

4. Using the SCAN (a.k.a. elevator) disk scheduling algorithm, determine how far the disk head moves servicing the following outstanding requests: 150, 19, 20, 900, 99. Assume the disk's head is currently over track 100 and moving toward smaller track numbers.  Also, assume that all of these track requests have already been received.

A. 962 tracks

B. 1064 tracks

C. 1681 tracks

D. 1863 tracks

E. None of these are true

 

5. If a process has allocated every 1024th virtual page (e.g. it has allocated virtual pages 0, 1024, 2048, 3072, 4096, 5120 ... 1024000), which one of the following page table schemes will use the LEAST amount of memory?

A. A flat page table

B. A two-level page table with 1024 first level entries

C. A two-level page table with 2048 first level entries

D. An inverted page table

E. Each of the above page table will use exactly the same amount of memory

6. Making no assumptions about the processes being scheduled, which of these scheduling algorithms will prevent starvation?

I. First Come First Served  (doesn’t work if a job runs forever—infinite loop)

II. Round Robin

III. Priority

 

A. I

B. II

C. I & III

D. I, II, & III

 

7. Consider a group of RAID4 disks. This group has four data disks and one parity disk. Which of the following are true?

I. Any data disk but NOT the parity disk can be reconstructed from the other four

II. The parity disk must be read whenever one of the data disks is read

III. The parity disk must be written whenever one of the data disks is written

 

A. III

B. I & III

C. II & III

D. I, II, & III

E. None of the above

 

8. Which of the following is true about two threads running in the same process?

A. One thread can both read and write another thread's registers

B. One thread can change the other thread's program counter

C. One thread can neither read nor write the other thread's stack

D. One thread can both read and write the other thread's stack (there is no address space protection between threads in the same process)

 

9.Which disk block allocation scheme will require the most I/O operations for random access to a large file?

A. Indexed allocation

B. Linked allocation

C. Contiguous allocation

D. I-node allocation

E. Each scheme requires approximately the same number of I/O operations

 

10. Which of the following does NOT solve deadlock?

A. Acquiring all resources before using any of them   (this is not acquiring all resources or no resources.  This doesn’t eliminate hold and wait)

B. Only acquiring resources in order based on a predetermined priority

C. Acquiring a maximum of one resource at a time (can’t have hold and wait if only have one resource)

D. If a resource is unavailable, releasing all resources and waiting for all required resources to become available

11. What is the primary reason that a translation lookaside buffer (TLB) is used?

A. A TLB ensures that a process does not access memory outside of its address space

B. A TLB makes translating virtual addresses to physical addresses faster

C. A TLB allows multiple processes to share the L1 cache

D. A TLB makes translating virtual addresses to physical addresses possible

E. None of the above

 

12. Which of the following is not a solution to thrashing?

A. Running fewer processes

B. Increasing the speed of the CPU

C. Increasing the size of physical memory

D. Rewriting programs to have better locality

E. These all solve the problem of thrashing

 

13. Which of the following is NOT a way to make file systems faster?

A. Put parts of a file on many different tracks so part of it can be accessed no matter where the disk head is

B. Cache frequently used blocks in memory so they can be accessed at memory speeds instead of disk speeds

C. Use a disk scheduling algorithm to minimize the distance between seeks

D. Put frequently used files or directories near the center of the disk so on average they won't be far from the read head

E. All of these will make a file system faster

 

14. Which of the following is true about base and bounds registers?

I. They offer protection between processes

II. They lead to internal fragmentation of physical memory

III. Once a process has been started at a given memory location, it cannot be moved to another location

 

A. I

B. II

C. I & II

D. I, II, & III

E. None of the above

 

15. Which of the following can I do without knowing your private key?

A. Pretend to send a private message on your behalf

B. Decrypt messages that were intended for only you

C. Send you a message that only you can read

D. Digitally sign a message on your behalf

E.  I must know your private key to perform all of these operations

 

16. Public/private key encryption is usually avoided because

A. It is much slower than symmetric key encryption

B. It is only useful when encrypting large amounts of data

C. It is not as secure as symmetric key encryption

D. It cannot be used unless two parties can exchange their private keys securely

E. None of the above

Suppose a system has only three physical pages. Given the following sequence of virtual page references, determine the number of page faults that are required. Initially, assume that the physical pages are not being used by any virtual page.

1 2 1 1 3 2 1 4 3 1 1 2 4 1 5 6 2 1

17. Using the first in first out (FIFO) replacement policy

A. 9

B. 10

C. 11

D. 12

E.  None of the above

 

18. Using the least recently used (LRU) replacement policy

A. 9

B. 10

C. 11

D. 12

E.  None of the above

 

 

19. Which of the following is NOT a use of TCP sequence numbers?

A. To ensure that data is delivered to the application in the order it was sent

B. To distinguish duplicate packets

C. To determine how much data is left to send

D. All of these are uses

 

20. Which of the following is NOT a property of Ethernet?

A. Nodes retransmit packets if there was a collision

B. Sending packets that are too big does NOT affect collision detection

C. Nodes retransmit packets if an acknowledgement is not received

D. After a collision, both nodes wait a random amount of time before retransmitting a packet

E. These are all properties of Ethernet