B1. A hard disk drive (HDD) is a data storage device for storing and retrieving digital information. The data are read and written to tracks on the magnetic disk as illustrated in Figure B1.1 by a head slider placed on the am controlled by the actuator motor. Rolation Spindle ar Disk cuator Track a Track b Head stider Arm (a (bi Figure B1.1. Overview of the computer hard disk construction Mageat Pesembly Vaice CeaActur Axism Figure B1.2. Details of the actuator based on the voice coil in a HDD