Magnetic Disk
A magnetic disk is a storage device that uses a magnetization process to read, write, rewrite and access data. Hard disk, Floppy disk and Zip disk are types of magnetic disk.
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| Figure: Cross Section of Hard Disk |
A
magnetic disk is a thin, circular metal plate. It is coated with a thin
magnetic film, usually on both sides. Digital information is stored on the
magnetic disk by magnetizing process.
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| Figure: Mechanical Structure of Magnetic Disk |
The disks
are mounted on a rotary drive so that the magnetized surface moves in close
proximity to magnetizing coil or head as shown in diagram.
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Figure: Magnetic Disk Read/Write Head |
The head
consists of a magnetic yoke and the magnetic coil. Digital information can be
stored on the magnetic film by applying current to the magnetizing coil. Head
is used for read and write data on magnetic disk.
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| Figure: Magnetic Disk Layout |
The data
on the disk is organized in a concentric set of rings as shown in diagram. This
concentric set of rings are called as track. The tracks are further divided in
to sector. Each sector stores a block of data which can be transferred to or
from the disk. Data bits are stored serially on each track. The same number of
bits are stored on each sector in a single track. To avoid magnetic
interference between two adjacent sectors the gap is introduced between two
adjacent sectors. Storage capacity of the track is increases as we move from
the inner most track to the outer most track.
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Figure: Working of Hard Disk |
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