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September 15, 2013

Essay on Hard Disk Drive

Hard Disk Drive
A hard disk is a magnetic mass memory used mainly in computers, but also in digital music players, camcorders, DVD player / recorder DVD, video game consoles, PDAs and mobile phones.
In a disk drive, there are rigid spinning plates. Each plate consists of a disc usually made of aluminum, which has the advantages of being lightweight and paramagnetic. More recent techniques use glass or ceramic, which allow states even smoother surface than aluminum. The faces of these plates are coated with a magnetic layer on which data is stored. This data is written in binary code [0,1] on the disk with a read / write very small antenna near the magnetic material. Next the electric current passes through it, the head modifies the local magnetic field to write either a 1 or a 0 on the surface of the disc. To read the same material is used, but in another sense: the movement of the local magnetic field leads to the terminals of the head an electric potential which depends on the value previously written, you can read a 1 or a 0.

A typical hard disk has a central axis around which the platters spin at a constant speed. All the read / write are connected to an armature that moves on the surface of the plates, with one to two head per plate (per side used a head). The armature moves the heads radially across the platters as they spin, allowing access to their entire surface.


Messmer, Hans-Peter (2001). The Indispensable PC Hardware Book (4th ed.). Addison-Wesley.


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