hard disk Rigid magnetic disk for storing computer programs and data. A built-in hard disk drive in a typical personal computer consists of a number of hard platters, coated with a magnetic material set on a common spindle. They are housed inside a sealed container, with a motor to spin the stack of platters, a head to write (record) and read (replay) each side of each platter, and associated electronic circuits. Hard disk capacity is continually being increased: most computers are now sold with a disk of at least 500Mb (500 megabytes, or 500 million bytes) capacity.

hard disk
1. A magnetic disk consisting of a rigid substrate coated or plated – usually on both sides – with a magnetic material. Hard disk is used as a generic term and includes the magnetic disks used in Winchester technology. Compare floppy disk, optical disk.

2. A disk permanently mounted in its drive; in certain circumstances disk + drive may be demountable.

hard disk • n. Comput. a rigid nonremovable magnetic disk with a large data storage capacity, as distinct from the smaller capacity floppy disk.