There are very few people who have seen a hard disk. Unlike floppy disks (or diskettes), hard disks are so delicate that they must be permanently placed in a protective aluminum casing. Everything you see, is the disk drive itself, a metal box with some circuits. There is no easy way to enter the box to see the disk: open the disc means contamination. The units should be opened only in clean rooms or rooms where workers wear suits surgeon and air is filtered to keep dust particles. Some discs are included in removable cartridges are inserted into the drive, but the majority are non-removable disk.
IBM invented the non-removable drives small and called by computer Winchester (apparently, because the code number of the unit coincided with the model number of a popular Winchester rifle). Tracks, sectors and heads on hard disk. Despite all this impressive armor, a hard disk is not very different from a floppy disk in the lower range. The data is written in the form of magnetic flux written in circles around the center ring of the disc. Each of the concentric circles form a track and each track is divided into an equal number of segments called sectors. The read / write moves from the outer edge of the disc to the center ring, standing on the track with the information needed by the computer. Once in position, the head waits for the correct sector runway is below it, and then reads or writes data to the industry as it passes underneath. Hard drive, CD, DVD, Floppy.
Hard drives are differentiated from other storage media, at densities for which data are recorded on the disc surface and the speed at which they operate. Unlike other media, the hard disk can contain up to ten times more data on each track. This density of data requires a head position read / write very small and very near the surface of the disc. Any flexibility that may be in the disc would make it leap and hit the read / write. For this reason the disc is made of a hard surface, using rigid aluminum plates coated with magnetic material. Company, Maxtor, Seagate, IBM, Hitachi, Toshiba, Quantum, Western Digital, Fujitsu, Samsung.