> Macs measure file sizes in powers of 10 and call them KB, MB, GB.

That doesn't conform to SI. It should be written as kB mB gB. Ambiguity will only arise when speaking.

> Advertised hard drives come in powers of 10.

Mass storage (kB) has its own context at this point, distinct from networking (kb/s) and general computing (KB).

> When you've got a large amount of data or are allocating an amount of space, ...

You aren't speaking but are rather working in writing. kb, kB, Kb, and KB refer to four different unit bit counts and there is absolutely zero ambiguity. The only question that might arise (depending on who you ask) is how to properly verbalize them.

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cornstalks 2 days ago | parent [-]

> That doesn't conform to SI. It should be written as kB mB gB

Little m is milli, big M is mega. Little g doesn’t exist, only big G.

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fc417fc802 2 days ago | parent [-]

Oh. Indeed you're correct. I was thinking in computer terms instead of scientific terms. Personally I see this as reinforcing that computers as a context wouldn't really benefit from using "proper" SI.

Note that no one is going to confuse mB for millibytes because what would that even mean? But also in practice MB versus Mb aren't ambiguous because except for mass storage no one mixes bytes with powers of ten AFAIK.

And let's take a minute to appreciate the inconsistency of (SI) km vs Mm. KB to GB is more consistent.

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nayuki 2 days ago | parent [-]

> no one is going to confuse mB for millibytes because what would that even mean?

Data compression. For example, look at http://prize.hutter1.net/ , heading "Contestants and Winners for enwik8". On 23.May'09, Alex's program achieved 1.278 bits per character. On 4.Nov'17, Alex achieved 1.225 bits per character. That is an improvement of 0.053 b/char, or 53 millibits per character. Similarly, we can talk about how many millibits per pixel JPEG-XL is better than classic JPEG for the same perceptual visual quality. (I'm using bits as the example, but you can use bytes and reach the same conclusion.)

Just because you don't see a use for mB doesn't mean it's open for use as a synonym of MB. Lowercase m means milli-, as already demonstrated in countless frequently used units - millilitre, millimetre, milliwatt, milliampere, and so on.

In case you're wondering, mHz is not a theoretical concept either. If you're generating a tone at say 440 Hz, you can talk about the frequency stability in millihertz of deviation.

	▲	fc417fc802 a day ago \| parent [-]
		Touche! I had no idea that term was in use. That said, I remain unconvinced that there is any danger of confusion here. Benchmarking compression algorithms is awfully specific; it's normal for fields to have their own jargon and conventions. > Just because you don't see a use for mB doesn't mean it's open for use as a synonym of MB. At the end of the day it's all down to convention. We've never needed approval from a standards body to do something. Standards are useful to follow when they provide a tangible benefit; following them for their own sake to the detriment of something immediately practical is generally a waste of time and effort. I don't believe I hallucinated unit notations such as mB and gB. Unfortunately I don't immediately recall where I encountered their use. > In case you're wondering, mHz is not a theoretical concept either. Just to be clear, I was not meaning to suggest that non-SI prefixes be used for quantifying anything other than bits. SI standardized prefixes are great for most things.