External Hard Drives – A Basic Explanation

If you’re a non-technical person who is new to computers or you struggle with computer terminology and jargon, this article provides a basic explanation of what an external hard drive is, why people buy them, and how you can determine if a particular hard drive will be compatible with your PC.

You will find information on specific hard drives on other posts in this blog, so feel free to poke around the site.

What is an External Hard Drive?

External Hard Drives - A Basic ExplanationA hard drive is a piece of computer hardware on which data (also known as files or software) can be stored. All PCs have a built-in hard drive, typically referred to as the “C” drive. Drives are generally assigned letters of the alphabet so the user and the computer can distinguish one from another.

An external hard drive is a hard drive that you buy separately and attach to your computer with a cable. When the hard drive is connected to your PC, you can add data to the external hard drive. You can access this data as long as the hard drive is connected to your PC. You can also delete and modify data once you’ve added it.

Other storage options are available, such as CDs and DVDs, but these hold very little data compared to an external hard drive. It’s generally a good idea to buy the largest hard drive you can afford, even if you can’t imagine needing that much extra space. Just like the closet space in your house, eventually you will fill it up.

Why do people buy external hard drives?

People buy external hard drives for a number of reasons, but the three most common are for:

  1. Extra storage
  2. Portable storage
  3. Backing up your “C” drive

We’ll discuss each of these in turn.

Extra storage

Today’s multimedia files (video and audio) can be fairly large and people tend to have a lot of them. Because your “C” drive contains a lot of other data (like your operating system), some people run out of room on the “C” drive and need an external hard drive to hold additional files. Of course you can store any type of data on an external hard drive. But typically people use them to store movies, video clips, and songs.

Portable storage

Some external hard drives (like the WD My Passport hard drives) are designed specifically to be portable, which means you can disconnect them from one computer and re-connect them to another computer. You may, for example, take your collection of movies to a friend’s house to watch. The hard drive needs to be compatible with both computers, which simply means that the external hard drive needs to be designed to work with both computers. We’ll talk more about compatibility later.

Computer backup

Suppose you have important files (like tax documents) or important software on your computer’s “C” drive. What happens if your “C” drive crashes? In many instances, your important files or software could be lost forever. When people want to protect important data from being wiped out, they will make a second copy for safe keeping on an external hard drive. If the files are extremely critical, the backup copy may be kept at another physical location. For example, suppose you experienced a fire or a flood. Both your primary copy and your backup copy could be destroyed.


Not every external hard drive will work with every computer. So when you buy an external hard drive, you need to make sure it will work with your PC as well as any other PC you may want to attach it to.

How the external hard drive connects to your PC

First, you need to be sure your PC and the external hard drive are able to physically connect to each other. As mentioned above, the external hard drive connects to the PC with a cable. The cable will have a connector on each end – one that plugs into your PC and the other that plugs into the external hard drive. Where you insert the connector is called a port.

There are many different types of ports. The most common types are USB (which stands for Universal Serial Bus) for PCs and Firewire for Macs. To make things even more complicated, different USB and Firewire ports can handle different capacities of data. For example, a USB 3.0 port can send and receive a lot more data at a faster rate than a USB 2.0 port (the higher the number, the newer the technology). One thing to be aware of is that ports are generally “backwards compatible”, meaning that you can plug a USB 2.0 connector into a 3.0 port. But you can’t plug a 3.0 connector into a 2.0 port.

So before you purchase an external hard drive, be sure to check the type and capacity of available ports on your PC and buy a drive with a compatible port. You may need to reference your PC manual to determine what kinds of ports are built into your machine.

Operating system software

The other compatibility-related consideration is your PC’s operating system. Not all external hard drives can work with all operating systems. However, most external hard drives can work with a variety of operating systems. In fact, many hard drives can work with PC or Macs.  As with cabling, you need to know your computer’s operating system and whether the external hard drive you are considering will work with it.

Keep in mind that this is a very basic explanation. There are other external hard drive characteristics you will want to consider before making a purchase. You can read about those by clicking here, but hopefully you now have a foundational base of knowledge to learn more about external hard drives.

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