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Computer Science IGCSEPDF 37
142 pagesrevision 46930
PDF 37
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Noise - Silent
Noise - Silent
Cost - Very low per gigabyte
Durability - No moving parts
Portability - Small and no moving parts
Capacity - Very low
Reliability - Prone to scratches
Speed - Very slow read/write access
➥ Optical Storage
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Virtual memory is an extension of RAM located on
secondary storage.
Opticalstorage uses lasers to store data.
The laser burns pits and lands on the disc’s surface to
represent binary 0s and 1s.
Optical devices use a laser to read and write data.
A moving arm directs the laser across the disk.
In CD-Rs, the laser burns pits and lands to store data.
The laser also reads data by detecting light reflections.
Scattered light at pit–land changes is read by a sensor as
binary data.
Advantages
Disadvantages
➤ Virtual Memory
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