Date: 15 Apr 2015

Magnetic disk is a fast secondary memory. It is a circular plate made up of metal or plastic coated with magnetized material. Usually both the sides of the plate are used. The disks are stacked on one spindle with read/write heads mounted on each surface. The disks rotate at high speed. Bits are stored in the magnetized surface in spots along concentric circles known as tracks. The tracks are divided into sectors. The minimum quantity of information transferred is a sector.