Hard disk. Simulated Xray of a hard disk memory mechanism from a computer. This consists of a readwrite head (pointed, black) on a rigid hard disk (upper centre), which is coated on both sides with magnetic material. The direction of magnetization of small localised areas of the disk represents the stored information in binary digits. Information is written and accessed by means of small electromagnets in the readwrite head. The disk rotates on a central spindle and the head moves radially to access different parts of the disk.
