Secondary Storage Devices

Question 1

Describe the principles of operation of an optical disk drive that is used to read data from an optical disk such as a CD-ROM or DVD-ROM.

Answer 1

Reading Mechanism:
1) Light is shone at disk.
2) Light focused on a spot on track.
3) Light is reflected back from disk.
4) Amount of light reflected back is measured.
5) Disc spins at constant linear velocity.

How data is represented:
1) Data is read in a spiral.
2) Land reflects light whereas pits scatter light.
3) Land represents 1, pit 0