A hard disk drive (HDD; also hard drive, hard disk, or disk drive) is a device for storing and retrieving digital information, primarily computer data. It consists of one or more rigid (hence “hard”) rapidly rotating discs (platters) coated with magnetic material, and withmagnetic heads arranged to write data to the surfaces and read it from them.
Hard drives are classified as non-volatile, random access, digital, magnetic, data storage devices. Introduced by IBM in 1956, hard disk drives have been the dominant device forsecondary storage of data in general purpose computers since the early 1960s. They have maintained this position because of advances which have resulted in increased recording capacity, reliability, and speed, as well as decreased cost, allowing them to keep pace with ever more demanding requirements for secondary storage