OS Input Output Systems

Question 41

The correct matching for the following pairs is

A. Activation record	  1. Linking loader
B. Location counter	    2. Garbage collection
C. Reference counts	    3. Subroutine call
D. Address relocation	  4. Assembler

• A-3, B-4, C-1, D-2
• A-4, B-3, C-1, D-2
• A-4, B-3, C-2, D-1
• A-3, B-4, C-2, D-1

Question 42

The concurrent programming constructs fork and join are as below: fork <label>         which creates a new process executing from the specified label join <variable>    which decrements the specified synchronization variable (by 1) and terminates the process if the new value is not 0. Show the precedence graph for S1, S2, S3, S4, and S5 of the concurrent program below.

   N = 2
   M = 2
   fork L3
   fork L4
   S1
L1:join N
   S3
L2:join M
   S5
L3:S2
   goto L1
L4:S4
   goto L2
next:

Question 43

A file system with a one-level directory structure is implemented on a disk with disk block size of 4K bytes. The disk is used as follows:             a) What is the maximum possible number of files? b) What is the maximum possible file size in blocks?

Question 44

Consider a storage disk with 4 platters (numbered as 0, 1, 2 and 3), 200 cylinders (numbered as 0, 1, … , 199), and 256 sectors per track (numbered as 0, 1, … 255). The following 6 disk requests of the form [sector number, cylinder number, platter number] are received by the disk controller at the same time: [120, 72, 2], [180, 134, 1], [60, 20, 0], [212, 86, 3], [56, 116, 2], [118, 16, 1] Currently head is positioned at sector number 100 of cylinder 80, and is moving towards higher cylinder numbers. The average power dissipation in moving the head over 100 cylinders is 20 milliwatts and for reversing the direction of the head movement once is 15 milliwatts. Power dissipation associated with rotational latency and switching of head between different platters is negligible. The total power consumption in milliwatts to satisfy all of the above disk requests using the Shortest Seek Time First disk scheduling algorithm is ______ . Note -This was Numerical Type question.

• 45
• 80
• 85
• None of these

Question 45

In __________ disk scheduling algorithm, the disk head moves from one end to other end of the disk, serving the requests along the way. When the head reaches the other end, it immediately returns to the beginning of the disk without serving any requests on the return trip.

• LOOK

• SCAN

• C-LOOK

• C-SCAN

Question 46

Suppose there are six files F1, F2, F3, F4, F5, F6 with corresponding sizes 150 KB, 225 KB, 75 KB, 60 KB, 275 KB and 65 KB respectively. The files are to be stored on a sequential device in such a way that optimizes access time. In what order should the files be stored ?

• F5, F2, F1, F3, F6, F4

• F4, F6, F3, F1, F2, F5

• F1, F2, F3, F4, F5, F6

• F6, F5, F4, F3, F2, F1

Question 47

A virtual memory system uses FIFO page replacement policy and allocates a fixed number of frames to the process. Consider the following statements M : Increasing the number of page frames allocated to a process sometimes increases the page fault rate N : Some programs do not exhibit locality of reference Which one of the following is true?

• Both M and N are true and N is the reason for M
• Both M and N are true and N is not the reason for M
• Both M and N are false
• M is false, but N is true

Question 48

A system uses FIFO policy for page replacement. It has 4 page frames with no pages loaded to begin with. The system first accesses 50 distinct pages in some order and then accesses the same 50 pages in reverse order. How many page faults will occur?

• 96
• 100
• 97
• 92

Question 49

Consider a disk sequence with 100 cylinders. The request to access the cylinder occur in the following sequence : 4, 34, 10, 7, 19, 73, 2, 15, 6, 20 Assuming that the head is currently at cylinder 50, what is the time taken to satisfy all requests if it takes 2 ms to move from one cylinder to adjacent one and shortest seek time first policy is used?

• 190
• 238
• 233
• 276

Question 50

Consider a disk system with 100 cylinders. The request to access the cylinders occur in the following sequences 4, 37, 10, 7, 19, 73, 2, 15, 6, 20 Assuming the head is currently at cylinder 50, what is the time taken to satisfy all requests if it takes 1 ms to move from one cylinder to adjacent one and shortest seek time first algorithm is used.

• 95 msec
• 119 msec
• 233 msec
• 276 msec