8.1 Hardware devices - Storage. Ranjit Bassi. Hard disk. The hard disk uses magnetic disk drives which allows rapid random access to large amount of data
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The hard disk uses magnetic disk drives which allows rapid random access to large amount of data
All disk drives use a thin circular platter made of non-ferrous metal or plastic and rotate it at up to 10,000 revolutions per minute beneath a read-write head that moves radially across the surface of the platter
The platter is coated with an emulsion of iron or cobalt oxide particles that act as tiny magnets
Binary data is recorded by aligning these tiny magnets in one direction to represent a binary 0 and in the opposite direction to represent a binary 1.
To read data stored on the hard disk, the read write head is moved to the desired track and waits for the relevant sector to pass beneath it.
In hard disk’s the greater amount of platters, the greater amount of storage capacity
NAND-type flash memory is a type of EEPROM which supports erasure of an individual block of memory cells
To alter the contents of a particular memory location, it copies the entire block into an off-chip buffer memory, erases the block, then rewrites the data back into the same block, making the necessary alteration to the relevant memory location
It requires a dedicated microprocessor with RAM buffer and this is included in a USB flash memory drive.
It can also be used as a music coded to turn a flash drive into an MP3 player