Digital Electronics: Principles, Devices and Applications

646 Digital ElectronicsFigure 15.32Internal structure of a typical hard disk.Corresponding tracks (blue)make a cylinderTrack nTrack 2Track 1SectorFigure 15.33Tracks and sectors in a hard disk.double-sided disk, the total number of sectors gets further multiplied by 2. From known values of thetotal number of sectors and the number of bytes stored per sector, the storage capacity of the disk inbytes can then be computed.There is a read/write head on one or both sides of the disk, depending upon whether it is a singlesidedor a double-sided disk. The head does not physically touch the disk surface; it floats over thesurface and is close enough to detect the magnetized data. The direction or polarization of the magneticdomains on the disk surface is controlled by the direction of the magnetic field produced by the writehead according to the direction of the current pulse in the winding. This magnetizes a small spot on