### The gigabyte myth

Jan. 5th, 2007 02:29 amOn New Year's Eve,

**leiju**came back to town (yay!) and we spent the evening at a dinner hosted by Jamie H. (doubling as his farewell party; he leaves for NJ on the 25th). One of the topics of conversation, also fresh in my mind from helping Astrid install a second HD into her computer, was that of why a hard disk never seems to be as large in the computer as it says it is on the box copy.

The answer is simple: normally, on box copy or advertising in general, there's a little footnote somewhere denoting "1 gigabyte = 1 billion bytes."

Computers? Don't think that way.

Don't forget, computers tend to think binary, so it's easier for them to compute volume in powers of 2. Thus, a kilobyte is actually 2

^{10}, or 1024 bytes. (There was a moment during the initial explanation where, since my cell phone's calculator wouldn't do repeats or exponents, I ended up doodling on the paper table cover to attempt to determine the different powers of 10. But I digress.) A megabyte would be 2

^{20}, or 1,048,576, bytes, and thusly, a gigabyte would be 2

^{30}, or 1,073,741,824, bytes.

Again, correct me if I'm wrong, but that's about 7% difference (1,000,000,000/1,073,741,824 = ~0.93) between a computer's and the box copy's perception of what a gigabyte is.

Because I think

**leiju**wants me to replicate the powers of 2, I'll put it

**( here, under this cut: )**

So, in a nutshell, that's why, whenever you pop in that brand new 80GB hard disk of yours, it says that that it has a capacity of 74.5GB in it.

This has been another...entry.