What is a Fixed Disk?

M. McGee

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.

A fixed disk, or hard drive, is an electronic storage medium.
A fixed disk, or hard drive, is an electronic storage medium.

Origins of the Term

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.

Most computers, as well as any device that features high-capacity storage, have one or more hard drive.
Most computers, as well as any device that features high-capacity storage, have one or more hard drive.

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.

Tablet computers use fixed disk drives.
Tablet computers use fixed disk drives.

How it Works

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.

Common Examples

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.

Risks and Precautions with Movement

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.

Capacity Designations

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.

In the early days of computer production, floppy disks were presented as the opposite of the fixed disk.
In the early days of computer production, floppy disks were presented as the opposite of the fixed disk.

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Discussion Comments


@parklinkz – Be careful when you carry that drive around. Hard drives are prone to fixed disk failures because of the way they’re made. I fix computers for a living, so I’ve seen a lot of damaged drives.

Don’t drop your disk drive, or the arms that write and read data to and from the disks could become damaged. If they can’t move properly, they won’t be able to access your data. It’s expensive to get the arms fixed, so make sure you keep your data backed up. That way, even if something happens to your drive, you won’t lose all your files.


@m3g4n – Wow! It’s amazing how far technology has advanced since I was a kid. Now, we have portable USB fixed disks that you can plug and unplug whenever you want. We’re so spoiled (I love it).

I carry a USB hard drive with me because I hate fiddling with CD burners. I use it to transfer audio files from my work computer to my home computer. I can’t email them to myself because they’re so big, so that’s my only option. I’m so glad my USB hard drive isn’t as big as a refrigerator!


I learned in computer class the other day that a fixed disk can also be called an HDD or hard disk drive. They were first made for use with mainframe computers back in the 1980s. They were huge, too. The first ones were as big as a refrigerator. They cost thousands of dollars back then.

Computers in the 1980s didn’t come with internal storage devices, because they were just too expensive. Everyone saved their files on those floppy disk things. If you didn’t save your work on a floppy before you shut your computer off, your work disappeared!

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