A disk is a circular platter constructed of metal or of plastic coated with a magnetizable material.
Data are recorded on and later retrieved from the disk via a conducting coil named the head.
During a read or write operation, the head is stationary while the platter rotates beneath it.
The write mechanism is based on the fact that electricity flowing through a coil produces a magnetic field.Pulses are sent to the head, and magnetic patterns are recorded on the surface below. The pattern depends on the positive or negative currents. The direction of current depends on the information stored , i.e., positive current depends on the information '1' and negative current for information '0'.
The read mechanism is based on the fact that a magnetic field moving relative to a coil produces on electric current in the coil. When the surface of the disk passes under the head, it generates a current of the same polarity as the one already recorded.