I wrote recently about how everything in computers is stored as 0s and 1s, and the language of computers is binary. You can read about that here. However, one bit or a few bits doesn’t really contain that much information. In general you will be dealing with thousands, or millions, or billions, or even more binary digits!

There are a set of prefixes that are associated with binary data, and here is what they all mean.

First a **bit** is just a single 1 or 0.

If you take 8 bits and put them together we call that a **byte**.

One thousand bytes is called a **kilobyte** (shorthand kB). The prefix kilo means 1,000, like kilogram. One minor thing is that computers always represent things in powers of 2, so although the prefix kilo means 1,000 on a computer it is more likely that a kilobyte is 1,024 bytes, because 1,024 = 2^10– the closest power of two to 1,000. A small text file on your computer is probably a few kilobytes up to a hundred kilobytes.

One million bytes is called a **megabyte** (shorthand MB). The prefix mega means 1,000,000. For a computer the exact number is the closest power of 2 which is 2^20. A standard mp3 file on your computer is probably somewhere from 3 to 10 megabytes (that is 3 to 10 MILLION bytes, or 24 to 80 MILLION 1s and 0s!).

One billion bytes is called a **gigabyte** (shorthand GB). The prefix giga means 1,000,000,000. For a computer the closest power of 2 is 2^30. A full-length video of medium quality is probably around a gigabyte in size.

Just for some more reference, the Google homepage just sent 32.1 kB of data. Just loading the home page of thekeesh.com was 440.98 kB, but doing it a second time was only 12.36kB of data. An image file in general is from tens of kilobytes to a few megabytes.

There are more prefixes bigger than giga–

**terabyte** is one thousand gigabytes

**petabyte** is one thousand terabytes

**exabyte** is one thousand petabytes

**zettabyte** is one thousand exabyte

**yottabyte** is one thousand zettabyte.

You can buy a terabyte hard drive these days for about $100 or less on a quick Google search, which is pretty crazy.

From the wikipedia page on zettabyte:

As of February 2012, no storage system has achieved one zettabyte of information. The combined space of all computer hard drives in the world was estimated at approximately 160 exabytes in 2006… As of 2009, the entire Internet was estimated to contain close to 500 exabytes. This is a half zettabyte.

So that is a basic introduction to some of the metric prefixes as applied to bytes.