1.2.9

Optical Storage & its Properties

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How Optical Storage Works

Optical storage uses laser light to retrieve data from the surface of optical media. Optical storage is often used to deliver multimedia content such as video.

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Storing a bit

  • Each 1 or 0 (value of a bit) is represented as a microscopic hole (called a pit) or a flat surface (called a land) on the surface of the disk.
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Accessing data

  • A laser is shone on the disk surface.
  • If the laser hits a land, it will be reflected into a sensor.
  • If the laser hits a pit, then it will be reflected elsewhere.
  • These can be used to represent our 1 and 0.

Properties of Optical Media

Optical media provides cheap and robust secondary storage.

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Low cost

  • Optical media is very cheap per-gigabyte (GB).
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Great reliability

  • Optical media is:
    • Waterproof.
    • Shockproof.
  • This makes it ideal for portability (transporting).
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Low capacity

  • Each disk has a low capacity.
  • Disks are small and fairly cheap. So it can be easy to gain a high capacity of storage by buying multiple disks.
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Low speed

  • Because the parts in the optical media drive have to move to find the right bit of data on the disk, access times can be quite slow.
  • Writing to a disk can also be a very slow process.

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1Computer Systems

1.1Systems Architecture

1.2Memory & Storage

1.3Computer Networks, Connections & Protocols

1.4Network Security

1.5Systems Software

1.6Ethical, Legal, Cultural & Environmental Concern

2Computational Thinking, Algorithms and Programming

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