Clearly describe how a hard disk from a computer works and also advancements in disk drive capacity.

Magnetic Marvels The hard-disk drive is a wonder of modern technology, consisting of a stack of disk platters, each one an aluminum alloy or glass substrate coated with a magnetic material and protective layers. Read-write heads, typically located on both sides of each platter, record and retrieve data from circumferential tracks on the magnetic medium. Servomechanical actuator arms position the heads precisely above the tracks, and a hydrodynamic air bearing is used to "fly" the …

…the introduction of a revolutionary technology from IBM. The innovation, based on the magnetoresistive effect (first observed by Lord Kelvin in 1857), led to a major breakthrough in storage density. Rather than reading the varying magnetic field in a disk directly, a magnetoresistive head looks for minute changes in the electrical resistance of the overlying read element, which is influenced by that magnetic field. The greater sensitivity that results allows data-storing domains to be shrunk further.