magnetic disc storage
Magnetic disk storage includes all drives that work with a fixed magnetic disk, i.e. hard disks, or with exchangeable magnetic disks, such as floppy disk drives. These storage media are block-oriented memories with random access.
In the case of magnetic disk storage, the data is stored in tracks that are located as concentric circles on the magnetic disk. The read/write head is guided in a radial direction to the selected tracks by means of a mechanical arm.
The number of tracks and the track spacing differ considerably in the various designs. At the current storage density, hard disks can have 15,000 to 20,000 tracks per inch, while removable disks have more than 100 tracks per inch. However, they are also fixed in track count because of their interchangeability.
The tracks of a magnetic disk are marked and addressed by a track address. The tracks in turn are divided into sectors, which are marked with the sector address. The beginning of the track, track 0, sector 0, is determined by the index marking on the diskette. Before a magnetic disk or floppy disk is used, the tracks and sectors are marked. This process is called formatting.