Gujarat University
MCA Semester III
Operating Systems
Date: 19th January, 2000 Marks:50
Instructions:
1. Answers to the two sections should be written in separate answer books.
2. Figure to the right indicates full marks.
3. You may make assumptions wherever necessary. Indicate clearly such assumptions you have made.
Section I
Q-1 State whether the following statements are TRUE or FLASE: [9]
1. Only one image (program) can be executed at any time in an active process.
2. Operating systems are fundamentally event-driven systems-they wait for an event to happen, respond appropriately to the event, then wait for the next event.
3. Multiple threads can read and write the same memory, whereas multiple processes can not directly read and write the same memory.
4. Again priority means the priority of a process decreases when it remains longer in Wait State.
5. Amongst the four necessary conditions for dead lock, no pre-emption condition means the process will not be preempted until termination.
6. TS (Test and Set) instruction makes it possible for only one process to receive a permit to enter its critical section.
7. If three processes P1, P2 , P3 arrive in this sequence and take 24, 3, 3 seconds for execution respectively, then mean waiting time will be 17 seconds.
8. I/O tasks are queued up by buffering and dispatched for execution by spooling.
9. Carving out a small partition from the unused space of a bigger occupied partition is known as internal fragmentation.
10. Translation look aside buffer (TLB) resides in physical memory and permits address translation from virtual to physical.
11. The NRU page replacement policy in virtual memory management scheme is a combination of FIFO and LRU policies.
12. Adding more physical memory to a process in virtual memory scheme generates more page faults for FIFO page replacement policy, which is known as Belady’s anomaly.
13. Rotational delay is the time spent waiting for the target sector to appear under the read/write heads of a disk drive.
14. Zombie is the name of a process state in Windows NT.
15. At least three different shells are available in any Unix System implementation.
16. The Unix command ‘grep’ stands for global register pointer.
17. A Trojan Horse software contains hidden code that when invoked performs some unwanted or harmful function.
18. Windows NT Wolfpack permits shared-nothing clustering of servers.
Q-2 Differentiate between a process and a thread. Which are possible operations that can be performed on
thread? Write uses and advantages of threads over processes. List the modern operating systems that support
threads. [8]
OR
Q-2 a) Why semaphores are used for mutual exclusion among an arbitrary number of processes? State the P and V
operations on semaphores. Also enumerate the hardware support developed for mutual exclusion in various
computer system. [4]
b) List the classical problems in concurrent processing. Write and explain refined algorithm of any one of these
problems. [4]
Q-3 Differentiate between pre-emptive and non-pre-emptive scheduling of processes. List all the process scheduling algorithms. Describe in detail the Multiple-Level-Queue (MLQ) scheduling algorithm. Indicate which operating system employs this algorithm. [8]
OR
Q-3 Explain briefly the following terms (any four): [8]
1. Interrupt and Trap
2. Buffering and Spooling
3. Monitors for process synchronization
4. Deadlock and Starvation
5. Static and Dynamic Priorities
6. Banker’s Algorithm
7. Turn-around Time, Waiting Time and Response Time
Section II
Q-4 What are the primary functions of memory manager in operating systems? Classify all the memory
allocation strategies. Describe fully the virtual memory management concept. Indicate use of Page Map Table and File Map Table in virtual memory management. Name three operating systems that have implemented virtual memory management. [8]
OR
Q-4 a) Describe the different approaches for selection of free areas of memory for creation of dynamic memory
partitions. Illustrate these approaches showing respective memory for the following incoming processes:
Arrival of process P and 14K followed by process Q of 20K.
The initial partitions are:
Used, 18K free, Used, 16K free, Used, 32K free, used, 28K free, Used. [4]
b) List the policy issues involved in management of virtual memory. Describe briefly the page replacement
policies which can be adopted in identifying a page for eviction. [4]
Q-5 a) Summarize the three techniques for performing I/O function within operating systems. Describe the DMA
technique briefly. [4]
b) Explain the terms- Seek Time, rotational Delay and Average Access Time of disk drives. Also list various
disk scheduling policies adopted by the disk controller. [4]
OR
Q-5 a) Indicate various types of threats to security of computer systems and networks. [4]
b) Illustrate the taxonomy of malicious programs that may affect the functioning of computer system or
network. Differentiate between Virus and Worm. Describe types of viruses and their detection/cure
approaches. [4]
Q-6 a) Define multi-processor systems. Show their classifications and advantages. Describe MIMD architecture in
detail. [4]
b) What is process Migration in Distributed systems? Which are different methods adopted for process
migration? Describe the Event Ordering algorithm. [5]
OR
Q-6 Define following terms (any six): [9]
1. Dirty bit 7. Inode
2. Dynamic Relocation 8. Microkernel
3. Thrashing 9. SMP
4. RAID 10. Zombie and Asleep states
5. Memory Hierarchy 11. Public and Private keys
6. Buddy System 12. LPC and RPC
