A hard drive can be compared to a small computer. It uses microprocessors to control both the physical behavior of the various electro-mechanical components. The logical operations that store and retrieve data as an arrangement of the magnetic particles on the disk surface. This operation is completely independent of the operation of the host PC. Like any computer, the hard drive needs its own software to control the operation of the microprocessors, but unlike a PC this software is limited to the drive’s operational functionality, and is not (and under normal circumstances cannot be) changed by the user. This hard drive ‘software’ is, as a result, more usually referred to as Firmware. The firmware carries out a range of functions, from what might be termed ‘Analogue’ functions such as controlling the spinning of the disc and positioning of the read/write heads, as well as the ‘Digital’ functions used to pass data files to and from the PC, keeping track of the location and parameters of the data files stored, and many, many more.
Without firmware, or the firmware is corrupted the drive is simply a collection of electronic components.