Storage Terminology (or What Does All This Talk About Bits and Bytes Mean?

Bits, Bytes, and all the other basic terms

Humans tend to (okay, we almost always) think about numbers in terms of base-10. It's probably because we have 10 fingers. Computers, on the other hand, don't. Instead, they think in base-2. That means that the only digits a computer really knows about are '1' and '0'.

The most basic unit of storage that a computer has is a bit. A bit is one binary digit, so it's either a '1' or a '0'. However, if someone wants to do anything useful with a computer, she would quickly discover that single bits don't do much good. They're just too small. So someone came up with the idea to call a string of 8 consecutive bits a byte.

Acronym	Full Term	What It Means	What it can store
n/a	bit	a zero or a one	Not much
n/a	byte	8 bits	A single character (e.g. 'a')
KB	kilobyte	2^10 = 1024 bytes	About a page of text
MB	megabyte	2^20 = 1024^2 = 1,048,576 bytes	One or two books
GB	gigabyte	2^30 = 1024^3 = 1,073,741,824 bytes	About half a movie
Kb	kilobit	1024 bits	1/8 a KB
Mb	megabit	1,048,576 bits	1/8 a MB
Gb	gigabit	1,073,741,824 bits	1/8 a GB

*Note, the last three terms have a 'b' instead of a 'B'. However, it gets more complicated when people are loose with their capitalization. What does someone mean by "kb"? Is it kilobyte or kilobit!?!?!? I MUST KNOW!!! There. See what happens with all this confusing jargon?

It's So Simple! What More Could There Be?

Yes. There is more. Sorry!! Unfortunately, some people (*cough* the hard drive industry *cough*) co-opted the standard terms kilobyte, megabyte, and gigabyte. They use the terms to refer to 1,000, 1,000,000, and 1,000,000,000 bytes respectively. Their reasons aren't really that complex, either. It allows them to "pad" the size of their drives.

They can market a 40 GB hard drive that actually can only store 40 billion bytes. However, this isn't what computers see. When you put this supposed "40 GB" drive into your computer, it won't see it as having 40 GB of free space. It will see the drive as having about 37.25 GB.

*Note, for reference, the calculation to arrive at the 37.25 GB figure was the following: (40*10^9) / (2^30)

The response to all this silliness was for some International Standards organization to adopt the terms kibibyte (KiB), mebibyte (MiB), and gibibyte (GiB). These are used to unequivocally refer to the power-of-two sizes. So if someone says kibibyte, you can be sure they're actually referring to 1024 bytes.

Although, I wouldn't pass it off the marketing folks to come up with some new way to co-opt the new terms!

So What Else Is There? Things like kbps or Mbps

I am so glad you asked! There are those things that combine the awesomeness of the things above (bits and bytes) with units of time (seconds, hours, days, years, minutes).

Let's break that down, shall we?

• The first two characters can be translated using the previous section. So the MB in MBps stands for megabyte.
• The second part just means "per second". You might see some other terms such as "ph" or "pm" ("per hour" and "per minute" respectively).

So if I said that my computer could send files at 2 bps, I would be saying that it was transfering two ones or zeroes per second (which is so slow that anything would probably be faster) One of the most common places you'll see these terms used is in referring to network devices. The specs of many of these devices say that they're megabit or gigabit ethernet. What they really mean is that they support transmitting a megabit or gigabit of information per second.

*Note that for network devices, the terms megabit and gigabit refer to 1,000,000 and 1,000,000,000 bits (not the nice power-of-twos from the table towards the top of this page).