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Bits, Bytes, and Beyond

My computer has a 200 GB hard drive. What’s GB stand for? What’s a MB? How much data can my computer hard drive hold?

If I asked you how many ounces are in a cup, you would be able to say that there are eight ounces in a cup and that would be it. And it should be that way for your hard drive question, right?

In a perfect world. We’re talking about computers, remember?

Let’s start with a list of prefixes:

kilo = meaning 1,000. (one thousand)
mega = meaning 1,000,000. (one million)
giga = meaning 1,000,000,000 (one billion)
tera = meaning 1,000,000,000,000 (one trillion)

So in answer to your question: GB is short for Gigabyte. MB is short for Megabyte. With a 200 Gigabyte (GB) hard drive, you have 200 billion bytes of data storage. If you had a 200 Megabyte hard drive, you have 200 million bytes of data storage.

Except that you don’t. You actually have more. (Huh?) Here’s how and why.

A byte (which stands for “BinarY digiT Eight.”) is a way to measure data storage. The first computers could only send 8 bits of data at a time, so it was natural to start writing code in sets of 8. Eight bits of data then became known as a byte. (By the way, a bit is represented with a lowercase “b,” whereas a byte is represented with an uppercase “b” (B). So Kb is kilobits, and KB is kilobytes.)

Computer data is measured using the Binary Code System (counted by factors of two: 1, 2, 4, 8, 16, 32, 64, etc), but the prefixes are based on the metric system! Hard drive manufacturers decided it would be easier to just go according to the way the metric system is supposed to work and – rather than give the exact amount of data storage – decided to round the numbers off, hence 1,024 bytes became 1,000 bytes.

Here’s the low end of the data measuring scale:

1 bit = a 1 or 0 (b)
4 bits = 1 nybble (which is ½ of a byte, meaning that two nybbles equal one byte (well, it depends on what you’re byting)
8 bits = 1 byte (B)

(Note that the very lowest measurement of data storage that a computer can recognize is a bit.)

And here’s how the scale progresses:


And more:


A couple of FYI’s:
All of the hard drives in the world combined do not add up to even one Zettabyte.
No computer in the world has yet to achieve a yottabyte of data storage.

So really – how much data can your 200GB hard drive hold?

You do the math. :)