HDD is the primary storage device in a computer system. It is responsible for storing all the data for the user and information related to system and the Operating System. It uses magnetic storage to store and retrieve digital information using one or more rigid rapidly rotating disks coated with magnetic material. Modern ultrabooks are being fitted with a static IC based storage instead of rotating disks. This increases energy and processing efficiency.
A hard drive has 2 main parts:
1. Rotating magnetic disk
2. A connecting circuit to motherboard of computer, which also provides power source to it