Hard Disk Drive(HDD)

A hard disk drive (HDD), usually referred to as a hard drive, hard disk, or fixed disk drive, is a non-volatile storage device which stores digitally encoded data on quickly rotating platters with magnetic surfaces. Severely speaking, "drive" refers to a device separate from its medium, such as a tape drive and its tape, or a floppy disk drive and its floppy disk. Early HDDs had detachable media; however, an HDD today is classically a sealed unit (apart from for a filtered vent hole to make equal air pressure) with fixed media.

The device that reads and writes data on a hard disk. Hard disk drives (HDDs) for PCs usually have sought times of about 12 milliseconds or less. Many disk drives improve their performance during a technique called caching.

There are more than a few interface standards for passing data between a hard disk and a computer. The most common are IDE and SCSI.

Hard disk drives are sometimes called Winchester drives, Winchester being the name of one of the first well-liked hard disk drive technologies urbanized by IBM in 1973.