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Why a kilobyte is 1000 and not 1024 bytes (zeta.one)

submitted 11 months ago by wischi@programming.dev to c/technology@lemmy.world

211 comments fedilink hide all child comments

I often find myself explaining the same things in real life and online, so I recently started writing technical blog posts.

This one is about why it was a mistake to call 1024 bytes a kilobyte. It's about a 20min read so thank you very much in advance if you find the time to read it.

Feedback is very much welcome. Thank you.

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[–] Australis13@fedia.io 10 points 11 months ago (12 children)

This whole mess regularly frustrates me... why the units can't be used consistently?!

The other peeve of mine with this debacle is that drive capacities using SI units do not use the full available address space (since it's binary). Is the difference between 250GB and 256GiB really used effectively for wear-levelling (which only applies to SSDs) or spare sectors?

[–] Lmaydev@programming.dev 11 points 11 months ago (2 children)

Power of 2 makes more sense to the computer. 1000 makes more sense to people.

[–] Australis13@fedia.io 6 points 11 months ago (1 children)

Of course. The thing is, though, that if the units had been consistent to begin with, there wouldn't be anywhere near as much confusion. Most people would just accept MiB, GiB, etc. as the units on their storage devices. People already accept weird values for DVDs (~4.37GiB / 4.7GB), so if we had to use SI units then a 256GiB drive could be marketed as a ~275GB drive (obviously with the non-rounded value in the fine print, e.g. "Usable space approx. 274.8GB").

[–] wewbull@feddit.uk 4 points 11 months ago

They were consistent until around 2005 (it's an estimate) when drives got large enough where the absolute difference between the two forms became significant. Before that everyone is computing used base 2 prefixes.

I bet OP does too when talking about RAM.

[+] wischi@programming.dev -9 points 11 months ago (1 children)

It's not as simple as that. A lot of "computer things" are not exact powers of two. A prominent example would be HDDs.

[–] Lmaydev@programming.dev 6 points 11 months ago* (last edited 11 months ago) (1 children)

In terms of storage 1000 and 1024 take the same amount of ~~bytes~~ bits to represent. So from a computer point of view 1024 makes a lot more sense.

It's just a binary Vs decimal thing. 1000 is not nicely represented in binary the same as 1024 isn't in decimal.

Edit: was talking about storing the actual number.

[–] abhibeckert@lemmy.world 4 points 11 months ago (1 children)

In terms of storage 1000 and 1024 take the same amount of bytes.

What? No. A terabyte in 1024 units is 8,796,093,022,208 bits. In 1000 units it's 8,000,000,000,000 bits.

The difference is substantial with larger numbers.

[–] Lmaydev@programming.dev -4 points 11 months ago* (last edited 11 months ago)

Both require the same amount of bits again. So the second one makes more sense for a computer.

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