Operating Systems (MC251) : October 2006

Section A : Basic Concepts (30 Marks)
1. Which of the following allows different parts of a single program to run concurrently?
(a) Multi programming (b) Multi Processing (c) Multi user (d) Multi threading (e) Multi tasking.
2. Which of the following is not the state of a process?
(a) New (b) Executing (c) Suspended (d) Waiting (e) Programming.
3. Which of the following denotes the function of Fork() method?
(a) Execute a program (b) Create a program (c) Suspend the process (d) Terminate the process (e) Swap a program.
4. An operating system is a
(a) Hardware (b) BIOS (c) Operator (d) Software (e) Firmware.
5. Graphical user interfaces (GUIs) make it easy for users to interact with the operating system by
(a) Using a light pen system
(b) Using finger as an input device
(c) Pointing cursor at icons and clicking on them
(d) Using specially programmed function keys on the keyboard
(e) Writing simple code using commands.
6. Which of the following becomes an important characteristic in the RR scheduling?
(a) CPU burst time (b) Time Quantum (c) Priority (d) Number of Processors (e) Number of Jobs.
7. Which one of the following is a synonym for Process Control Block?
(a) Process Blocking (b) Control Blocking (c) Task control block (d) Disabled block (e) Interruption.
8. Acronym for IPC is
(a) Internet Protocol Control (b) Interface Process Communication (c) Intranet Program Control (d) Internet Process Control (e) Inter Process Communication.
9. Which of the following is a technique of gradually increasing the priority of processes that wait in the system for a long time?
(a) Starvation (b) Dispatcher (c) Blocking (d) Termination (e) Aging.
10. A device driver is a
(a) Process State (b) Queue (c) person (d) program (e) Peripheral.
11. Which of the following describe the deadlocks more precisely?
(a) Pie graph (b) Resource Allocation graph (c) Bar graph (d) Gantt graph (e) XY graph. 12. Which one of the following is not a condition for deadlock?
(a) Mutual Exclusion (b) Progress (c) Hold and Wait (d) No preemption (e) Circular Wait.
13. Which of the following is an external criteria for assigning a priority to a job?
(a) Memory Requirements (b) Number of open files (c) I/O burst time (d) Political factors (e) Time limits.
14. Acronym for TLB is
(a) Translation look-side buffer
(b) Translation look buffer
(c) Translation level buffer
(d) Translation look-aside buffer
(e) Translation load-side buffer.
15. Which of the following is/are non self modifying code(s)?
I. Machine code.
II. Critical section code.
III. Reentrant code.
(a) Only (I) above
(b) Only (II) above
(c) Only (III) above
(d) Both (I) and (II) above
(e) Both (I) and (III) above.
16. Which of the following defines the term “Roll back”?
(a) Terminating (b) Blocking (c) Undoing (d) Redoing (e) Creating.
17. Identify the disadvantage of main memory caches.
(a) Permit workstations to be diskless
(b) Data can be accessed more quickly
(c) Performance speedup in bigger memories
(d) Permits a single caching mechanism for servers and users
(e) Time consumed for recovery.
18. Access-right =
(a) (b)
(c) (d) (e)
19. Which of the following is not a System Threat?
(a) WORM (b) Denial of Services (c) Internet WORM (d) Viruses (e) Trojan Horse.
20. Consider the following figure to identify the disk scheduling algorithms among the given options.
(a) SCAN (b) SSTF (c) C-SCAN (d) C-LOOK (e) LOOK.
21. How many different levels are used to arrange RAID?
(a) 4 (b) 6 (c) 5 (d) 3 (e) 8.
22. Which of the following is not a file attribute?
(a) Name (b) Protection (c) Security (d) Size (e) Location.
23. Consider the following figure to identify the disk allocation techniques among the given options.
(a) Sequential Allocation (b) Indexed Allocation (c) Linked Allocation
(d) Contiguous Allocation (e) Blocked Allocation.
24. Block number =
(a) (number of bits per word) * (number of 0-value words) + offset of first 1 bit
(b) (number of bits per word) +(number of 0-value words) * offset of first 1 bit
(c) (number of bits per word) * (number of 0-value words) / offset of first 1 bit
(d) (number of bits per word) / (number of 0-value words) + offset of first 1 bit
(e) (number of bits per word) * (number of 0-value words) * offset of first 1 bit. Answer >
25. Which of the following is a block of available memory?
(a) Break (b) Segment (c) Allocated partitions (d) Hole (e) Sector.
26. Acronym for PTLR is
(a) Page Table Link Register
(b) Partition Table Load Register
(c) Page Table Length Register
(d) Process Table Length Register
(e) Page Table Length Relocation.
27. Which of the following is the type of Semaphore?
(a) Sorting Semaphore (b) Counting Semaphore (c) Calculating Semaphore (d) Manipulative Semaphore (e) Derived Semaphore.
28. Which of the following is not a problem of Synchronization?
(a) Bounded Buffer (b) Readers-writers (c) Dinning philosopher
(d) Dinning Professor (e) None of the above.
29. High-level synchronization construct that allows the safe sharing of an abstract data type among concurrent processes is
(a) Monitor (b) System (c) MOS (d) Counter (e) Multi threading.
30. Acronym for RMI is
(a) Remote Method Implementation
(b) Remote Memory Invocation
(c) Real time Method Invocation
(d) Remote Method Invocation
(e) Reliable Method Invocation.
Section B : Problems (50 Marks)
1. Draw the state transition diagram of a process and label each state and each transition in the diagram. Briefly explain the transitions and the queues in which the process will be waiting.
(10 marks)
2.
a. Mike, the manager, has the right to read and change any files in his company. Tom is one of the team leaders in the company. He has the right to control all files in the team and read other teams’ file only. Tom has three assistants Jim, David and John. Each of them is working on a project. The assistants can read and execute others’ work in the team, but they cannot write in it or access the files of other teams. Now, you are the system administrator of the company. Set the access permission for them in UNIX.
b. From the below figure, Compute the average waiting time for the FCFS and SRTF scheduling.
(6 + 4 = 10 marks)
3.
a. What is the main characteristic of TLB (Translation Lookaside Buffer) in memory management unit of an Operating-System?
b. If a memory reference takes 800 nanoseconds; a TLB reference takes 60 nanoseconds; and the hit-rate is 95%, what is the effective memory reference time? How much speed-up we gained using TLB technique compared to the pure paging with no TLB? Show your calculations below. (4 + 6 = 10 marks)
4. Consider five processes P0 to P4 that use four resource types with the following snapshot
at time t0. Answer the following questions:
Allocation A B CD Request A B CD Available A B CD
P0
0 1 0 2
0 2 0 0
4 0 0 3
P1
2 0 0 1
1 0 1 1
P2
1 0 1 0
0 1 0 1
P3
2 1 0 1
0 0 0 0
P4
0 0 2 1
0 0 3 1
a. In the context of deadlock detection, do the processes need to declare the number of resources they NEED to complete their work (Yes or No)? Why?
b. In the above table, briefly explain whether the following equation among the matrices is correct or not? Allocation + Request = Maximum need
c. Most of the current operating systems only rely on “deadlock detection” mechanism not the deadlock prevention or avoidance. Why?
d. At time T1 > T0 process P0 requests 3 resources of type C and process P3 requests 2 resources of type A. The operating system does not grant the resource requests before time T2 T1. Below draw two tables that show the changes that will occur at “time T1” and at “time T2”.
e. At time T2 the operating system also applies the deadlock detection algorithm. If the system is in the deadlock situation, determine the processes involved in the deadlock and the value of the vector Available. If the system is not in deadlock indicate the sequence of changing the values of vector Available and its final value (3 + 3 + 3 + 6 + 5 = 20 marks)
Section C : Applied Theory (20 Marks)
5.
a. For contiguous, linked and indexed disk allocation techniques specify its characteristics in terms of:
1. Ease of growth of file size.
2. How the free disk blocks are assigned.
3. Ease of random access to a location in a file.
4. Advantages and disadvantages.
b. Name four items in the Process Control Block (PCB). (6 + 4 = 10 marks)
6. What are the main characteristics of the following types of operating systems in terms of resource utilization and the type of services they provide?
a. Batch Processing Systems.
b. Time Sharing Systems.
c. Personal Computers.
d. Handheld Computers. (10 marks)
Suggested Answers
1.
Answer : (d)
Reason: Multi threading allows different parts of a single program to run concurrently.
2.
Answer : (e)
Reason: Programming is not the state of a process.
3.
Answer : (b)
Reason: Fork() is a command to Create.
4.
Answer : (d)
Reason: An operating system is Software.
5.
Answer : (c)
Reason: Graphical user interfaces (or GUIs) make it easy for users to interact with the operating system by pointing at icons and clicking on them.
6.
Answer : (b)
Reason: The RR scheduling depends on the Time Quantum.
7.
Answer : (c)
Reason: Process Control Block is also called as Task control block.
8.
Answer : (e)
Reason: IPC stands for Inter Process Communication.
9.
Answer : (e)
Reason: Aging is a technique of gradually increasing the priority of processes that wait in the system or a long time.
10.
Answer : (d)
Reason: A device driver is a program.
11.
Answer : (b)
Reason: Deadlocks can be described more precisely in terms of a graph called Resource Allocation graph.
12.
Answer : (b)
Reason: Progress is not a condition for deadlock.
13.
Answer : (d)
Reason: Political factors is a external criteria for assigning a priority to a job.
14.
Answer : (d)
Reason: TLB stands for Translation look-aside buffer.
15.
Answer : (c)
Reason: Reentrant code is a non self modifying code.
16.
Answer : (c)
Reason: Roll back is Undoing a process.
17.
Answer : (e)
Reason: The disadvantage of main memory caches is Time Consumed (high) for recovery.
18.
Answer : (a)
Reason: Access-right =
19.
Answer : (e)
Reason: Trojan Horse is not a System Threat but program threat.
20.
Answer : (c)
Reason: illustrates C-SCAN
21.
Answer : (b)
Reason: RAID is arranged in 6 different levels.
22.
Answer : (c)
Reason: Security is not a file attribute.
23.
Answer : (b)
Reason: illustrates Indexed Allocation.
24.
Answer : (a)
Reason: Block number =(number of bits per word) * (number of 0-value words) + offset of first 1 bit.
25.
Answer : (d)
Reason: Hole is a block of available memory.
26.
Answer : (c)
Reason: Acronym for PTLR is Page Table Length Register.
27.
Answer : (b)
Reason: Counting Semaphore is the type of a semaphore.
28.
Answer : (d)
Reason: Dinning Professor is not a problem of Synchronization.
29.
Answer : (a)
Reason: High-level synchronization construct that allows the safe sharing of an abstract data type among concurrent processes is Monitor.
30.
Answer : (d)
Reason: Acronym for RMI is Remote Method Invocation.