Operating Systems 2066

Section-A

Attempt any two questions:   (2x10=20)

1.  Define the term semaphore. How does semaphore help in dining philosophers problem? Explain.

2. Explain how does file allocation table (FAT) manage the files. Mention the merits and demerits of FAT system. A 200 GB disk has 1-KB block size, calculate the size of the file allocation table if each entry of the table has to be 3 bytes.

OR

Suppose that a disk drive has 100 cylinders, numbered 0 to 99. The drive is currently serving a request at cylinder 43, and previous request was at cylinder 25. The queue of pending request, in FIFO order is:

86, 70, 13, 74, 48, 9, 22, 50, 30

Starting from the current head position, what is the total distance (in cylinders) that the disk arm moves to satisfy all pending requests for each of the following disk scheduling algorithms?

a.  FCFS

b.  SCAN

3.      Write short notes on :

a.  Least recently used page replacement algorithm

b.  Segmentation

c.  Associative memory

Section-B

Attempt any eight questions:   (8x5=20)

4.      What is an operating system? Differentiate between time sharing and real time operating system.

5.      Why thread is necessary? In which circumstances user-level thread is better that Kernal level thread?

6.      Explain about hierarchial directory systems with diagrammatic examples.

7.      How can you define the term process scheduling? Differentiate between I/O bound process and CPU bound process.

9.      What do you mean by interrupt? Explain the working mechanism of interrupt controller.

10.      Define the term indefinite postponement. How does it differ from deadlock?

11.      Explain the mapping of virtual address to real address under segmentation.

12.      Compare the throughput (overall performance) of SCAN with SSTF.