Secondary Storage

Question 1

Describe how optical storage functions.

Answer 1

Bits are represented on a disk by pits and lands.
A laser shines on the disk as it spins at a constant linear velocity.
The amount of light reflected back is measured.
Transitions between pits/lands scatters light (1).
Continuation of pits/lands reflects light (0).

Question 2

Principles of operation of magnetic storage?

Answer 2

‘Disc’ is made up platters.
These platters have iron particles which can be magnetised to represent 1 or 0.
The disk spins at constant linear velocity (6000rpm).
Read/write arm moves head over surface of disc.
Data is read/written using electromagnets.

Question 3

Principles of operation of solid state storage?

Answer 3

Transistors arranged in grid layout.
NAND and NOR gate used to control flow of electrons.
Current flowing if 1 and not if 0.