Section 17.2
Review Questions
Disk Drives
  1. What secondary storage device holds virtually data and programs for most computers?
answer...
disk drives
  1. What size were the original floppy disks?
answer...
8 inches in diameter
  1. What do we call the round things that actually store the data?
answer...
platters
  1. In a hard disk drive, do the read/write heads actually touch the surfaces?
answer...
no, they ride a few thousandths of an inch above, suspended on a cushion of air
  1. How fast are the surfaces spinning in hard drives?
answer...
Usually at least 3000 rpms (revolutions per minute) but some disks are spinning at 7000 rpm. The fastest in 1997 was a Seagate drive spinning at 10,000 rpm.
  1. How do bits actually get stored on a hard disk's surface?
answer...
An electromagnetic field is set up through the coil in the read/write head and this aligns the tiny regions of magnetizable paint into the same directions.
  1. What is the motor called that moves the head back and forth across the surface?
answer...
stepper motor
  1. How is data stored on a hard disk's surface? Circle one: 
               in a spiral              in concentric circles
answer...
in concentric circles
  1. Is there just one read/write head?
answer...
Sometimes in cheap drives, but today not usually. Today there is one head per surface.
  1. What is the fundamental unit of storage area on the surface of a disk?
answer...
sector
  1. How big are sectors?
answer...
From 512 bytes on up, almost always in multiples of 1K, such as 1K, 2K, 4K, 8K. 512 bytes is 0.5K
  1. Is every single square inch of a surface used for data in a disk drive?
answer...
Definitely not; there are dead spaces between the sectors that allow for the electronics to rest and find the beginning of the next sector. There are also unused regions between the concentric tracks. These are areas where the stepper motor does not stop so the read/write head is never over them for long, certainly not long enough to read or write data.