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KiB � Kilobinary Byte. See http://physics.nist.gov/cuu/Units/binary.html for more definitions.

I recently bought a 120 GB harddisk and it was only 111 GiB, so since then I try to use the “new” abbreviations.

It really does not make any sense :( especially since the harddisk also came with 8 MB cache, so did they actually mean 7.6 MiB cache? The harddisk industry sucks! :)


I don’t really know why this is such a big deal to so many people. In fact, there was that whole recent law-suit against a bunch of computer venders because users thought that they were trying to deceive them. It all is because the users didn’t understand this difference. They were not, in fact, being ripped off.

If the drive was 120 GB, it is 120 GB. Just because your computer returns the number in GiB doesn’t mean that you were ripped off.

It would be nice if the correct abbreviation were used by the user-level applications on an OS. I suppose the educating enough developers about this should resolve the problem, in time.


I think the problem is that since the birth of the computer, data storage has always been reported in power of twos, i.e. kilo being 2^10, mega being 2^20 and giga being 2^30. It is the only storage measurement that makes sense and harddisk sizes were also reported using this scheme, afterall, a file has the same size wether it is on disk or in memory. And if we need to transfer it over a 10 MBit line and the size is 5 MBit it should take half a second – we should not mix up what the prefixes means.

Then I think it was in the beginning of the 90’ties harddisk manufactorers started to sell 512 MB harddisks which were really 488 MiB (before that the reported size was in MiB IIRC), i.e. they even ensured that the size of the fake megabytes was a power of two, clearly deceptive IMHO (today they no longer do that though) – and it later became the standard for harddisk sizes to be reported (by manufactorers only, not the operating systems) as small megabytes (and later gigabytes).

In 1998 we then got a standard saying that the old KB, MB, GB etc. should now refer to the small sizes (power of ten) and we got new abbreviations for the power of two.

But we really ought to have gotten new abbreviations for the power of ten prefixes, which then the harddisk manufactors should use, and the rest of the world could stay with the abbreviations which have been in use since the birth of the computer.


The decision to change the powers of two was the better decision since Ki, Mi, etc only are used in size representations on computers. Real-life measurements are done in powers of ten.

It was incorrect of them to ever say that a kilobyte was 1024 bytes. The prefix “kilo” means “one thousand.”

I would hate to see people changing all maps, tools, measuring devices, etc to use new abbreviations simply because a few programmers didn’t won’t to change a line of code so that their users wouldn’t be confused.

It’s pretty unambiguous, because it will always prefix bit or byte – also, ‘a few programmers’ is the entire industry and accademic world for the last 40 years or so, and nothing would have to be changed if we stayed with kilo meaning 1024 when prefixing bit or byte.