Ubuntu Policy: prefixes for multiples of units

Martin Pitt martin.pitt at ubuntu.com
Thu Sep 25 12:30:55 BST 2008

Scott James Remnant [2008-09-24 20:28 +0100]:
> > > Since a byte is not divisble by 10, and a bit is inherently indivisible,
> > > the divisor prefixes: deci(d), centi(c), milli(m), micro(µ), nano(n),
> > > pico(p), femto(f), atto(a), zepto(z) and yocto(y) are *not* valid and
> > > must never be used in Ubuntu.
> > 
> > Not true. There are statistical circumstances in which these terms
> > make sense, in the same way that we talk about fractions of a person.
> > 
> Given that we're attempting to convey information to the user, and that
> very few users would be familiar with the term "nanobyte" or the
> implications of it, is it really worth allowing?

I agree that it largely doesn't make sense. A millibit by itself is
bogus, but millibits per second has quite an obvious meaning
(although I hope that nobody's internet access will really be that
slow :) ).

Since I never actually saw a practical case, I agree that we can
discourage the use of fractional prefixes in the policy.

> The great thing about standards is that there as so many to choose from.
> One standard defines 1024 bytes as a kibibyte (the IEC one) and another
> as 1.024 kilobytes (the ATAPI one).

Hm, there's obviously a typo here (1024 bytes != 1024 kilobytes), I'm
just not creative enough to figure it out.

> My only and overriding concern is that if a user buys something that
> says "80 GB" on the box, then Ubuntu says "80 GB" when asked about it.
> Not "74 GiB", not "74 GB" and not "80 GiB".

Of course 80 GiB and 74 GB would be actively wrong. Displaying it as
74 GiB would be correct, but since hard drives are generally
advertised in GB nowadays (i. e. 10^12 bytes), file managers should
stick to that standard.

> I'm not sure how desirable or worrying it is for an Ubuntu machine to
> report 2.1GB of RAM when a user just bought 2GB, and it quite clearly
> said 2GB on the box.

That's just because the box is wrong then, and it is *not* 2 GB. It's
2 GiB, and that's what Ubuntu should report for the special case of
RAM (where you can't actually buy powers of ten for technical


Martin Pitt                        | http://www.piware.de
Ubuntu Developer (www.ubuntu.com)  | Debian Developer  (www.debian.org)
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