Hard disk is made of metal & is usually rigid/ firm.
Hard disk is not removable like the floppy disk, but it is fixed inside the computer. However, it works on the same basic principles as the floppy disk.
A hard disk is made up of one or more platters (disk plates), arranged one on top of the other to form a disk pack. The platters are made from a metallic material, usually an Aluminum alloy or Glass in order to make them light.
The glass platters have enough Ceramic within it to resist cracking & also they can better resist the heat produced during operation.
Each platter is coated on both sides with a magnetic material, usually Iron Oxide, which enables data to be recorded on the platter. This is why many platters are brownish orange in colour.
The mixture (of the magnetically sensitive substance) is poured on the platter, then spinned to evenly distribute the film over the entire platter.
The disk pack plates are held on a rotational Spindle, which is used by the drive motor to rotate the plate surfaces past the Read/write heads in order for the read & write operations to be performed on the recording surfaces.
Data is written on & read from the disk using Read/write heads in the disk drive, under the influence of the computer’s command signals.
The heads are attached to a device or an access arm called the Head Actuator, which is used to move the read/write heads across the platters to the destination track.
There is usually 1 Read/write head on each side of a platter & all the heads are attached to a single actuator shaft so that the heads move in unison. Each head has springs to force it into the platter it reads.
When off, the heads float between the surfaces of the platters, which are held in a vacuum that enables it to spin/ rotate around very quickly.
When the drive is running, the platters rotate causing air pressure that lifts the heads slightly off the platter surface. The disk rotates & the heads can move in & out over the surface to record or read data on the various tracks.
Notes.
- The Read/Write heads do not touch the disk plate’s recording surface. They fly over to avoid the R/W head’s ‘crash’, which may result in the wearing away of the magnetic coating over the recording surfaces that may cause loss of the recording property of the magnetism.
- The distance between the head & the platter is very small such that the drive must be assembled & repaired in a very clean room because one dust particle can throw the whole drive off.
Kavungya answered the question on
April 2, 2019 at 08:03