Storage Devices

Are those which are permanently stored programs and data needed by the central processing unit, CPU for its operations and processes as opposed to main memory where programs and data are stored temporarily and are lost as soon as you turn the computer off , storage units can be recorded programs and data over time, until they are deleted or removed by action necessary for that purpose. Currently three technologies are basically used to store information:

Magnetic Technology:
The surface of the storage media is coated with magnetic material (similar to the magnets), sensitive to the magnetic field.The units have magnetic read heads - writing, they contain electromagnets that generate a magnetic field to be traversed by a magnetic current in the recording process, the heads are a current, magnetizing particles of the medium and record and information. The main storage media are floppy disks, hard disks and magnetic tapes.
Optics:
Optical storage technique locates the information by laser, consisting of a light beam focused and coherent approach that allows very small areas accurately. When the disc spins at high speed some areas reflect the laser light into a sensor, while others disperse.Within the major optical media are compact disk or CD, and DVD (Dynamic Versatility Disc).
Magneto-optical (MO):
This technology combines the advantages of magnetic media with the optical. A MO disc is an optical disc capacity and ease of rewriting magnetic media. MO disks are currently available in various sizes and capacities, its appearance is very similar to floppy disks (diskettes), but have vastly superior capabilities and require a special device, called ZIP, for reading and writing.