A hard disk drive, or HDD, is a component of a computer that stores data and software applications. The HDD is a metal platter with a magnetic coating that stores data, and a read/write head that accesses the data while the platters are spinning.

The vast majority of PCs have an HDD inside them, though there are some more specialized devices that don’t. Tablets and smartphones, for example, typically have a much smaller storage capacity and don’t use an HDD.

HDDs come in a variety of sizes, with the smallest being around 2.5 inches in diameter and the largest being …