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Why a kilobyte is 1000 and not 1024 bytes

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.

unreasonabro ,

i mean, you can't get to 1000 by doubling twos, so, no?

Reality doesn't care what you prefer my dude

smo ,

This has been my pet rant for a long time, but I usually explain it .. almost exactly the other way around to you.

You can essentially start off with nothing using binary prefixes. IBM's first magnetic harddrive (the IBM 350 - you've probably seen it in the famous "forklifting it into a plane" photo) stored 5 million characters. Not 5*1024*1024 characters, 5,000,000 characters. This isn't some consumer-era marketing trick - this is 1956, when companies were paying half a million dollars a year (2023-inflated-adjusted) to lease a computer. I keep getting told this is some modern trick - doesn't it blow your mind to realise hdd manufacturers have been using base10 for nearly 70 years? Line-speed was always a lie base 10, where 1200 baud laughs at your 2^n fetish (and for that matter, baud comes from telegraphs, and was defined before computers existed), 100Mbit ethernet runs on a 25MHz clock, and speaking of clocks - kHz, MHz, MT/s, GT/s etc are always specified in base 10. For some reason no-one asks how we got 3GHz in between 2 & 4GHz CPUs.

As you say, memory is the trouble-maker. RAM has two interesting properties for this discussion. One is that it heavily favours binary-prefixed "round numbers", traditionally because no-one wanted RAM with un-used addresses because it made address decoding nightmarish (tl;dr; when 8k of RAM was usually 8x1k chips, you'd use the first 3 bits of the address to select the chip, and the other 10 bits as the address on the chip - if chips didn't use their entire address space you'd need to actually calculate the address map, and this calculation would have to run multiples of times faster than the cpu itself) . The second, is that RAM was the first place non-CSy types saw numbers big enough for k to start becoming useful. So for the entire generation that started on microcomputers rather than big iron, memory-flavoured-k were the first k they ever tasted.

I mean, hands up who had a computer with 8-64k of RAM and a cassette deck. You didn't measure the size of your stored program in kB, but in seconds of tape.

This shortcut than leaked into filesystems purely as an implementation detail - reading disk blocks into memory is much easier if you're putting square pegs into square holes. So disk sectors are specified in binary sizes to enable them to fit efficiently into memory regions/pages. For example, CP/M has a 128-byte disk buffer between 0x080 and 0x100 - and its filesystem uses 128-byte sectors. Not a coincidence.

This is where we start getting into stuff like floppy disk sizes being utter madness. 360k & 720k were 720 and 1440 512-byte sectors. When they doubled up again, we doubled 2800 512-byte sectors gave us 1440k - and because nothing is ever allowed to make sense (or because 1.40625M looks stupid), we used base10 to call this 1.44M.

So it's never been that computers used 1024-shaped-k's. It should be a simple story of "everything uses 1,000s, except memory because reasons". But once we started dividing base10-flavoured storage devices into base2-flavoured sectors, we lost any hope of this ever looking logical.

unreasonabro ,

2, 4, 8, 16, 32, 64, 128, 256, 512, 1024. It's pretty fucking logical m8. You know what's not logical? Base 10

SmartmanApps ,
@SmartmanApps@programming.dev avatar

Yeah, base ten really screws around with programming. You specifically have to use a decimal type if you really want to use it (for like finance or something), but it's much slower.

gens ,

The mistake is thinking that a 1000 byte file takes up a 1000 bytes on any storage medium. The mistake is thinking that it even matters if a kB means 1000 or 1024 bytes. It only matters for some programmers, and to those 1024 is the number that matters.

Disregarding reality in favor of pedantics is the real mistake.

billwashere ,

Well it’s because computer science has been around for 60+ years and computers are binary machines. It was natural for everything to be base 2. The most infuriating part is why drive manufacturers arbitrarily started calling 1000 bytes a kilobyte, 1000 kilobytes a megabyte, and 1000 megabytes a gigabyte, and a 1000 gigabytes a terabyte when until then a 1 TB was 1099511627776 bytes. They did this simply because it made their drives appear 10% bigger. So good ol’ shrinkflation. You could make drives 10% smaller and sell them for the same price.

wischi OP ,

Pretty obvious that you didn't read the article. If you find the time I'd like to encourage you to read it. I hope it clears up some misconceptions and make things clearer why even in those 60+ years it was always intellectually dishonest to call 1024 byte a kilobyte.

You should at least read "(Un)lucky coincidence"

billwashere ,

Ok so I did read the article. For one I can’t take an article seriously that is using memes. Thing the second yes drive manufacturers are at fault because I’ve been in IT a very very long time and I remember when HD manufacturers actually changed. And the reason was greed (shrinkflation). I mean why change, why inject confusion where there wasn’t any before. Find the simplest least complex reason and that is likely true (Occam's razor). Or follow the money usually works too.

It was never intellectually dishonest to call it a kilobyte, it was convenient and was close enough. It’s what I would have done and it was obviously accepted by lots of really smart people back then so it stuck. If there was ever any confusion it’s by people who created the confusion by creating the alternative (see above).

If you wanna be upset you should be upset at the gibi, kibi, tebi nonsense that we have to deal with now because of said confusion (see above). I can tell you for a fact that no one in my professional IT career of over 30 years has ever used any of the **bi words.

You can be upset if you want but it is never really a problem for folks like me.

Hopefully this helps…

https://lemmy.world/pictrs/image/50f959aa-ed61-4f20-b4aa-66b3729ad1c4.jpeg

CallumWells ,

I just think that kilobyte should have been 1000 (in binary, so 16 in decimal) bytes and so on. Just keep everything relating to the binary storage in binary. That couldn't ever become confusing, right?

rottingleaf ,

Because your byte is 10 decimal bits, right? EDIT: Bit is actually an abbreviation, BIT, initially, so it would be what, DIT?.. Dits?..

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