HDD stands for Hard Disk Drive, which is a non-volatile data storage device that uses magnetic storage to store digital data and fetch it using rotating platters. It is an electromechanical device having non-volatile memory and is used as the primary storage device in a computer system. HDDs are capable of storing operating systems, large system files, and are found in desktops, mobiles, and consumer electronics. The two most common form factors for modern HDDs are 3.5-inch, for desktop computers, and 2.5-inch, primarily for laptops. HDDs are connected to systems by standard interface cables such as PATA (Parallel ATA), SATA (Serial ATA), USB, or SAS (Serial Attached SCSI) cables. The HDD form factor refers to the physical size or geometry of the data storage device. Having an industry-standard form factor helps determine a common compatibility with different computing devices.