There are one or more platters in a hard disk, each platter being a non-flexible disk that is coated with the iron-containing "paint" mentioned above. Oftentimes the platters are coated on both sides in order to double the storage capacity.

Read-write heads are suspended above the platters' surfaces, riding on a micro-thin cushion of air that is generated when the platter spins at enormous rates, usually 3000 to 7000 rpm (revolutions per minute). These read-write heads contain wires that are coiled into a tiny electromagnet at the tip.