What is a Fixed Disk?

A fixed disk, also called a hard drive or a hard disk drive, is a high-capacity magnetic storage device that is permanently installed inside of a computer, smartphone, or high-capacity portable music player, and is also usually the onboard storage mechanism for most gaming consoles. These disks come in a variety of shapes and sizes, but most work in the same basic way. They maintain working files and permanent memory loads while serving as an anchor for the device’s operations and applications.

The name “fixed disk” was very common when it was first introduced in the 1950s, but grew progressively less popular as they years passed. Though the term still has some relevance, it is often referred to in common speech simply as a “hard drive.” In the past, there were many ways of storing information outside of a computer, but very few ways of storing information internally. The term implied that the disk was fixed in place inside the computer and couldn’t just be taken out like other forms of storage could. The term “hard disk” took prominence when these became common in home computers. These were considered the opposite of a floppy disk, the common removable storage media of the time.

Fixed disks became increasingly popular as the need to store data outstripped the storage media of the time. They were considered by many to be very slow and expensive, however. It was not until the cost came down and the storage capacity increased that they became a regular part of consumer electronics; at first, they were installed only in large corporate computers and industrial machines. Over time, the capacity of the drives increased and their physical size decreased. Most experts now consider them to be one of the most cost-effective means of data storage and they are be found in many hand-held devices, including many MP3 players, smartphones, and tablet computers.

The inside of a fixed drive is basically the same across any size or configuration. An internal motor causes very thin magnetic platters to begin spinning. These platters are covered in tiny magnetic regions that each have a directional charge, and when they spin that charge gains traction and its signal can be converted by the computer’s circuitry and motherboard into meaningful data and direction.

Another internal motor runs one or more arms that move around the platters. The “read” arm reads the directional charge and sends the information out of the drive. The “write” arm, on the other hand, changes the directional charges, saving and storing new information on the platter. The inside of one disk may look very different from another in a different device, but all of these basic parts are typically there.

Hard drives in computers are some of the most common examples. Nearly every modern computer has one or more of these drives that store all of the computer’s saved information, including operating system data, applications, documents, and photos. Any electronics with high-capacity storage typically have these, too, though usually on a smaller scale. The fixed disk in an MP3 player is usually a lot smaller than one on a desktop computer, for example, but they usually work in the same way and often closely resemble each other, though one is necessarily smaller than the other. They are also found in most digital video recorders, gaming consoles, and home media centers, and most modern smartphones contain them, as well.

Fixed disks typically work best when they are not outwardly moving, and in most traditional computers they aren’t — they are situated on a desk, on a table, or in an otherwise stationary office space. With increasing mobility comes increased risk of damage, though. Tablet computers, smartphones, and portable music players are just a few examples of devices with fixed drives that move a lot almost by design. A traditional disk would not do well under these circumstances, and there is always a risk that either the read or write arms can fall off track with too much jostling. In most cases, though, devices that are prone to movement also have protective casings and extra strengthening around their drives to help prevent disk slippage or other harm.

Most hard disks are categorized in terms of storage capacity, and the relevant unit is usually the byte. A byte is generally understood to encompass eight bits, and traditionally it took one byte to encode each letter of computer code. The first computers had disk capabilities measured in kilobytes, which is to say, 1,000 bytes of data. Next came megabytes (1,000² bytes, followed by gigabytes (1,000³ bytes) and terabytes (1,000⁴ bytes). The specific number is an indication of how much memory or storage space is available for applications, files, and other documents that can be saved and quickly retrieved. In most cases the larger the memory space on a drive the more expensive it is, though not always. A lot depends on the market and the precise capabilities of the device at issue.