Cambridge O Level Computer Science · Syllabus 2210 · Hardware
Optical Storage
What is Optical Storage?
Optical storage is secondary storage in which data is held as pits and lands along a spiral track on a disc, read by a laser that reflects differently from the two surfaces.
This definition is part of the Hardware chapter in Cambridge O Level Computer Science.
Optical Storage in context
Optical storage uses lasers to create and read pits and lands on the surface of a disc. A pit is a small indentation; a land is the flat surface between pits. When the laser shines on the surface, a pit and a land reflect the light differently, and the difference is interpreted as the binary values. The examples named by the syllabus are CD, DVD and Blu-ray.
Questions students ask about Optical Storage
What is the difference between magnetic, optical and solid-state storage?
Magnetic storage, such as a hard disk drive, uses electromagnets in a read/write head to magnetise regions of a spinning platter in one of two directions, representing 1s and 0s. Optical storage, such as a CD, DVD or Blu-ray, uses a laser to read pits and lands on a disc's surface, which reflect light differently. Solid-state storage, such as an SSD, SD card or USB flash drive, has no moving parts and stores data by trapping electrons on floating gate transistors using NAND or NOR flash technology.