The mechanism that reads and writes data on a hard disk. Hard disk drives (HDDs) for PCs generally have seek times of about 7 to 12 milliseconds or less. Many disk drives improve their performance through a technique called caching. 

There are several interface standards for passing data between a hard disk and a computer. The most common are IDE , SCADA and SCSI.

Hard disk drives are sometimes called Winchester drives , Winchester being the name of one of the first popular hard disk drive technologies developed by IBM in 1973.