Disk Scheduling - 2 - Operating System Questions & Answers

1.

Whenever a process needs I/O to or from a disk it issues a ______________

   A.) system call to the CPU
   B.) system call to the operating system
   C.) a special procedure
   D.) all of the mentioned

Answer: Option 'B'

system call to the operating system

2.

If a process needs I/O to or from a disk, and if the drive or controller is busy then :

   A.) the request will be placed in the queue of pending requests for that drive
   B.) the request will not be processed and will be ignored completely
   C.) the request will be not be placed
   D.) none of the mentioned

Answer: Option 'A'

the request will be placed in the queue of pending requests for that drive

3.

Consider a disk queue with requests for I/O to blocks on cylinders :
98 183 37 122 14 124 65 67
Considering FCFS (first cum first served) scheduling, the total number of head movements is, if the disk head is initially at 53 :

   A.) 600
   B.) 620
   C.) 630
   D.) 640

Answer: Option 'D'

640

4.

Consider a disk queue with requests for I/O to blocks on cylinders :
98 183 37 122 14 124 65 67
Considering SSTF (shortest seek time first) scheduling, the total number of head movements is, if the disk head is initially at 53 :

   A.) 224
   B.) 236
   C.) 245
   D.) 240

Answer: Option 'B'

236

5.

Random access in magnetic tapes is _________ compared to magnetic disks.

   A.) fast
   B.) very fast
   C.) slow
   D.) very slow

Answer: Option 'D'

very slow

6.

Magnetic tape drives can write data at a speed ________ disk drives.

   A.) much lesser than
   B.) comparable to
   C.) much faster than
   D.) none of the mentioned

Answer: Option 'B'

comparable to

7.

On media that use constant linear velocity (CLV), the _____________ is uniform.

   A.) density of bits on the disk
   B.) density of bits per sector
   C.) the density of bits per track
   D.) none of the mentioned

Answer: Option 'C'

The farther a track is from the center of the disk.

8.

SSTF algorithm, like SJF __________ of some requests.

   A.) may cause starvation
   B.) will cause starvation
   C.) does not cause starvation
   D.) causes aging

Answer: Option 'A'

may cause starvation

9.

In the ______ algorithm, the disk arm starts at one end of the disk and moves toward the other end, servicing requests till the other end of the disk. At the other end, the direction is reversed and servicing continues.

   A.) LOOK
   B.) SCAN
   C.) C-SCAN
   D.) C-LOOK

Answer: Option 'B'

SCAN

10.

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

   A.) LOOK
   B.) SCAN
   C.) C-SCAN
   D.) C-LOOK

Answer: Option 'C'

C-SCAN

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