A hard disk drive contains an integrated recording media as well as the interface mechanism necessary to access and manipulate it. It typically occupies an internal drive bay, but may also be an external unit, connected to the computer through |cables|. The drive uses |read-write heads| to recognize and manipulate the magnetic data on the media. A motor spins the disks so that the read/write head can access the |data sectors|.
The large storage capacity and quick access make hard drives almost required equipment. They allow the use of large programs without the interchange of |disks| necessary with |floppy disk| systems. Hard disks commonly have capacities ranging from 20 |megabytes| to several hundred megabytes, though some can store a |gigabyte| or more.
