My old 20gB hard disk was about to pack up, so I bought a 320gB disk from PC World for £64.99 (£1 is roughly equivalent to US$2 at the time of writing, so it’s roughly worth $130).
The disk was advertised as being 320gB. Which was around 23gB from the truth. And sadly, I can’t sue PC World or Hitachi under the Trade Descriptions Act.
So why are they able to get away with such a monstrosity? The short answer is that there’s a common (and widely exploited) misconception about the true values of a gigabyte, megabyte etc. Read on for the long answer.
Ah. You carried on. That’s nice. So, down to business – what is this megabyte thing anyway?
Data on computers is stored in bits – a compression of binary digits. A bit is one value – it can be either a 0 or a 1. Eight bits is equal to one character encoded using a system called ASCII, or equivalent to one modern byte.
A kilobyte (abbreviated as kB) is 1024 characters in ASCII, therefore is 1024 bytes. Why 1024, I hear you cry?
Well, as everything in computers is in twos, 1 byte×2×2×2×2×2×2×2×2×2×2 (or 210) is equal to 1024. That’s why memory is bought in 128mB, 256mB, 512mB and 1024mB modules instead of the more logical (to us at least) 125, 250, 500 and 1000.
A megabyte (mB) is 1024 kilobytes, or 1048576 bytes. A gigabyte is 1024 megabytes, or 1073741824 bytes.
Here is where the problem lies. A kilobyte is roughly 1000 bytes, but not exactly – and the mass media commonly reports the value of the kilobyte to be 1000 bytes, not 1024. Computer and hard disk manufacturers exploit this misconception, and calculate a kilobyte as 1000 bytes, not the true value of 1024.
Most major operating systems, however, calculate it as 1024 bytes to the kB, and so on. So you’ll actually lose something like 24 bytes for every kilobyte, and when that goes up into the gigabytes, that’s an awful lot.
Tags: don't be stupid, Hardware, oops, pedantry, storage
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Could you tell me what the blog’s font is?
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As far as I can tell it’s Lucida Sans or Lucida Grande.
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This is how ALL hard drives are sold. They ALWAYS tell you the size in Billions of bytes, and call it a Gigabyte. It just so happens that it’s more convenient for an operating system to look at it as 2^30 bytes = 1GB instead. Surprisingly, this is not their fault at all, and is in fact your own fault for being stupid.
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This is how ALL hard drives are sold.
Well, they shouldn’t be.
Surprisingly, this is not their fault at all, and is in fact your own fault for being stupid.
Yes, but I’ve been called up by novices before who claim that a hacker has destroyed their hard disk/they’ve been mis-sold the hard disk. Then you have to explain to them that 2^30b=1gB, not 10^9b, and that some space will be taken up by the OS, etc etc. Remember that computer novices often don’t read the small print.
It would be better, I think, if advertisements stated ‘about’ or ‘almost’ [insert disk size in billions of bytes here]. Or if they just counted in 2s when making the things.
I do believe that this should be properly explained to consumers BEFORE they buy a disk.
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A giga of anything is 10^9, whether it be bits, bytes, grams, chairs, etc. So, their drives are in fact 320 gigabytes, but only about 298 gibibytes. 1 gibibyte = 1024^3 bytes = 2^30 bytes.
The definition of giga shouldn’t change just because you’re talking about computers.
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