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Optical Media
Key Revision Points
Optical Media
 In size order:
 CD – 700MB
 DVD – 4.7GB
 Blu-Ray – 25GB
 Variations: Each of the above can come in 3 formats:
 ROM e.g. BD-ROM Read Only
 R e.g. DVD-R Can be written to once
 RW e.g. DVD-RW Rewritable (can write to many times)
 All optical media work on the same principle
 Learn these steps!
 Data on the CD/DVD/Blu Ray stored as microscopic indentations called pits
 Disk spins
 Arm/rail containing a laser moves in and out over the spinning disk
 A laser beam is shone onto the disk where it hits a pit or land(flat area)
 The reflected beam translated into binary
Relatively Cheap (per GB of data)
Low capacity compared with modern
USB flash drives
Increasing Internet speeds have made
cloud storage an alternative for
backing up personal data
Water/shock proof
Easily scratched
Textbook and Firefly
 Textbook page 7