Hard Disk Drive

A hard disk drive (HDD) is an electro-mechanical data storage device. It is also called fixed disk, hard disk, hard drive. It is used to store all data on a computer (such as documents, movies, songs, pictures, software etc). It is a type of non-volatile storage, retaining stored data even when powered off.  Nowadays, it is typically in form of a small rectangular box

For examples, look HDD(Hard Disk Drive) in below picture:

Fig: Hard Disk Drive (HDD)

There are two types of HDD. They are:

(1)    PATA Hard Disk

(2)    SATA Hard Disk