Re: Using standardized SI prefixes

[Ivan Jager <aij+nospam@andrew.cmu.edu>]

On Fri, 15 Jun 2007, Ben Finney wrote:
> Ivan Jager <aij+nospam@andrew.cmu.edu> writes:
> > On Thu, 14 Jun 2007, Ben Finney wrote:

[re added the relevant quote]
> > > The difference being that digital specifications for things like
> > > storage capacity and memory are not measured. They are calculated, and
> > > in those contexts they *are* precise.

> > > Since we *can* give a perfectly precise quantity of bytes and
> > > other digital phenomena, and often do, this is even more reason to
> > > use the precise meaning of the units for those quantities.
> >
> > Ok, so this applies to dd and what else?
>
> It applies to any software that refers to quantities that use these
> units. Pick a unit for the quantity, base-10 or base-2, and use its
> precise meaning and the precise term for it.

I think you missed the point. The only times it is not rounded is when the 
user is specifying a size. (And even then it is sometimes rounded.)

> > I thought this argument was mostly about measured sizes anyways,
> > such as what you would get from ls -lh, df -h, du -h, or their GUI
> > equivalents. These are all rounded.
>
> Any time the software says "GB" when the quantity was actually
> calculated in 2^30, or says "GiB" when the quantity was actually
> calculated in 10^9, the units are mismatched. Whether the quantity was
> rounded is irrelevant to this fact.

It was relevant enough for Alex to say sizes aren't rounded... 
Yes, accuracy, precision, and ambiguity are all separate things. Rounding 
is not completely irrelevant though, since most of the time "1 GB" is 
correct, "1 GiB" is also correct.

Ivan