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Solid state disc drive

Computers have a (secondary) storage device called a disk drive, It is where all your apps are stored. There are currently two types of storage device, the magnetic hard disk drive and the solid state disk drive.

A computer (unopened)
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A computer (opened) - SSD shown
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SSD removed
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How does a solid state drive work?

  1. When you take the cover off a solid state drive/USB memory stick, you will see NAND flash memory cells (as below)
  2. Inside NAND flash memory cells are billions of "Floating gate transistors" arranged as a grid
  3. Floating gate transistors (are a bit like cups that) trap electrons in a "pool"
Opening data from a SSD
  1. When opening data from a SSD, if one floating gate transistor contains electrons, the computer reads it as a "zero". If another floating gate transistor is empty of electrons, the computer read it as a "one"
Saving to a SSD
  1. When saving data to a SSD, an electrical charge (from the computer) is used to create binary string which is sent to the SSD. A charge causes electrons to move between two pools
Deleting/erasing data from a SSD 
  1. To erase data from a SSD, a high voltage removes electrons from the pools.

​NAND flash memory magnified

NAND flash (black chip)
​
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NAND magnified (one small section shown)
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NAND magnified further to show one of billions of the floating gate transistors
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Examples of solid state media

Picture
Memory card and and smart phone memory
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USB memory stick
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Tablet computer memory
Loading Solid state drive
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