While we're being pedantic: I agree with you about SI prefixes, but bits are indivisible. A millibit doesnt exist (only possible use would be if one was referring to something like a transfer speed as "19 millibits per second", but that's kind of lacking meaning - "0.019 bit per second" or "1.14 bits per minute" would be better)

> bits are indivisible

No, they're not. Sure, in more familiar scenarios where you're measuring the size of some amount of data it's an integer, but there's nothing mathematically wrong with having a not-integer number of bits.

See: https://en.wikipedia.org/wiki/Shannon_(unit)

If you do any sort of calculations with information theory you're quite likely to end up with a non-integer number of bits, and there's nothing wrong with that.

You can absolutely have two ranges which require 7.5 bits to store each (0-180) and write them to 15 bits of storage.

Just because physical hardware is more or less restricted to integer bit quantities doesn't mean fractional bits aren't a useful concept.

Sure, I accept I was wrong, and millibits may have some niche usage. That said, the comment I was responding to was describing hardware with "4 mb" of ram. There's no confusion in that case.

Also in older texts MB often refers to MiB. Even today there are context where people nearly always mean MiB even when they write MB.

Where does mebibyte come into play?

Mebibyte comes from pedants (like myself) that say that the Mega prefix in SI means 10^6, but in computing we often take it to mean 2^20. Mebibyte is unambiguous, and if everybody used it (unlikely. I don't think either MacOs or Windows use it), then Mega would also be. Right now, when you see mega in a computing context you're not sure if it means 10^6 or 2^20, although a lot of times it doesn't even matter.

It wouldn’t make sense for macOS to use the binary prefixes for file sizes, as it uses the decimal sizing method to show file sizes.

Okay, this is second hand as I don't own a mac, but a friend who does noticed that on his macbook, macOS reports file sizes with megabyte being 10^6 bytes, whereas windows follos the 2^20 convention.

He was going crazy over a file being shown as 600Mb on Windows and 629Mb on mac. When he compared the bytes values, they were the same (around 629,145,600 bytes) and that settled it.

They changed the behavior of macOS a number of years ago (2012?) because disk manufacturers advertise storage capacity in 10^x, and the operating system displaying sizes in 2^y made the disks seem smaller and (in theory) caused confusion.

My MacBook Pro's internal "1 TB" disk is actually 1,000,240,963,584 bytes -- neither 1 TB nor 1 TiB.

I remember this. The packaging showing the calculation that 1MB = 1024 bytes

> He was going crazy over a file being shown as 600Mb on Windows and 629Mb on mac. When he compared the bytes values, they were the same (around 629,145,600 bytes) and that settled it.

To be fair: It make sense to measure RAM in MiB, because it is addressed by binary address lines so you always end up with a power of two.

Files are, however, as big as somebody decided to write into them (modulo some rounding to the next sector, depending on file system implementation details). It does not make much sense to measure them in MiB. Quite often it just more confusing to calculate file sizes in MiB instead of MB. I dont even know why Microsoft stated that MiB business.

Similar with hard disks by the way. They contain as many sectors as the manufacturer was able to put on them. There is no power of two involved.

Possibly interesting: https://developer.apple.com/documentation/foundation/bytecou...

This is true, macOS reports it using decimal sizing.

I believe the reason is that all storage devices are marketed in decimal sizes anyway.

"Mebibyte" and similar units were only coined in 1998, a few years after the era of 4mb/8mb graphics cards.

kB = KiloByte mB = MegaByte