Ubuntu Policy: prefixes for multiples of units

Scott James Remnant scott at canonical.com
Wed Sep 24 20:28:36 BST 2008

On Wed, 2008-09-24 at 12:16 -0600, Neal McBurnett wrote:

> On Wed, Sep 24, 2008 at 06:26:12PM +0100, Scott James Remnant wrote:
> > We've had an unofficial policy about this for a while now, but since we
> > have the Ubuntu Policy manual
> >
> > <http://people.ubuntu.com/~cjwatson/ubuntu-policy/> I'd like to make
> > this more official by including it there.
> I've never heard of this sort of unofficial policy - where has it been
> documented?
That's kind of the point of an unofficial policy, it's never been
documented, we've just practised it.

> > First we should have the discussion.
> Note the existing discussions: 
>  https://bugs.launchpad.net/ubuntu/intrepid/+source/net-tools/+bug/240073
>  https://bugs.edge.launchpad.net/ubuntu/+source/net-tools/+bug/119998
Indeed, and your comments on those discussions were right in front of me
as I attempted to write this up.

Unless I'm mistaken, the following largely agrees with you?

> > 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?

> > Confusion has often reigned as to the exact values of these multiples;
> > since computing has often used factors as powers of 2, rather than
> > powers of ten.  Thus a kilobyte may be considered 1x2^10 bytes (1024) or
> > 1x10^3 bytes (1000) depending on the system in use.
> > 
> > Efforts have been made in the standardisation world to address this
> > problem.  The International Electrotechnical Commission (IEC), in IEC
> > 60027-2 A.2, invented a new set of "binary" prefixes.  These include the
> > kibibit, mebibit and gibibit.
> > 
> > Despite their attraction to the standards world, these have not yet seem
> > adoption in the industry.
> On the contrary, in addition to support from multiple international
> standards bodies (IEEE, ISO, IEC, NIST and CENELEC), there are many
> software applications that use these prefixes - see:
>  http://en.wikipedia.org/wiki/Binary_prefix#Software
You realise that almost none of those are outside of the FLOSS world, or
anywhere else that the user may have come across before?

> > Ubuntu policy is to use the prefix and factor that matches a user's
> > expectation based on their purchase.
> Abandoning sensible international standards, and basing our software
> instead on the whims of marketing people writing advertising copy for
> packaging, which varies by manufacturer and time and culture, will
> cause us much chaos.
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).

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".

> It is much more important that the ubuntu user not get confused about
> internal inconsistencies, and e.g. misconfigure their backups or swap
> space.
> Users will encounter a discrepancy between a quoted size on a box vs a
> number that shows up via ifconfig only once, but if we use "Giga"
> inconsistently, they will have to deal with figuring out how to
> correct for those internal inconsistencies every time they use their
> system.
I'm quite happy to agree on using Giga consistently to mean 1x10^9,
however I was mindful of your comment that RAM manufacturers (and
standards!) still build in powers of two.

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.

Though given RAM manufacturers now make disks (SSD), anyone know what
they use? :p

Scott James Remnant
scott at canonical.com
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