Unit Converter

[JohnGray]

Alan

Your reference is about the best I've ever found, too, other than The NisT Reference on Constants, Units, and Uncertainty, which says: "Because the SI prefixes strictly represent powers of 10, they should not be used to represent powers of 2. Thus, one kilobit, or 1 kbit, is 1000 bit and NOT 2^10 bit = 1024 bit." (and it gives your reference near the bottom)

I also think the standard SI prefixes for multiples of ten are flawed. All those with powers of ten from 6 upwards bear a capital letter, whereas all those with negative powers of ten bear a lower-case letter. The rule should really have been that "positive powers of ten bear a capital letter". The major exception is kilo (k), which should really be K. I ignore hecto (h), which is rarely seen and should also be H, and deka (da) which I've never seen used and is the only prefix with two letters!

It has been put to me that the argument about whether a Megabyte is a thousand or 1024 Kilobytes "depends on whether you are buying or selling"! How often have you bought a hard disk advertised as (say) 120 MB, and found out that when you formatted it it came down to just over 114 Real Megabytes?

John

[Bowlie]

When you order wine by the glass in <img src=/S/flags/Switzerland.gif border=0 alt=Switzerland width=18 height=18> you order it by the deci(litre). Deux deci du Gamay, s'il vous plait?

[JohnGray]

May be, but I was talking about deka, 10 litre units!

(Perhaps you were, too?) But it would have been of Liebfraumilch, or Piat D'Or, perhaps...

John

[Bowlie]

deci, deca - c'est la meme chose! la la la <img src=/S/cheers.gif border=0 alt=cheers width=30 height=16> <img src=/S/cheers.gif border=0 alt=cheers width=30 height=16> <img src=/S/drop.gif border=0 alt=drop width=23 height=23>

[bigaldoc]

<hr>...bought a hard disk advertised as (say) 120 MB, and found out that when you formatted it it came down to just over 114 Real Megabytes...<hr>

And, if you lay aside all the VALID mathematician and scientist lingo, below is an example of what "normal" computer users encounter on a daily basis. I sometimes wish Windows would stop the "rounding off" crap (that's what I call it). I for one would never quote a 6.75 GB number - useless drivel...

[JohnGray]

Al

I'm not sure what point you're making! Are you saying that the total should have been to two decimal places also, rather than the three significant figures which all three values had?

Surely the information for the end user should have been:
"Your hard disk is getting dangerously short of free space, and you ought to buy another (or a bigger) one before installing any new Microsoft product"!

John

[bigaldoc]

I knew I probably shouldn't have jumped in at this point, John. Sorry for the confusion. My only point was that the red-boxed numbers are of no use to ME and I would never quote them to anyone as they are too "rounded off" for MY tastes, i.e. 1,024 x 1,024 x 1,024. For example, in a recent thread about my work with TrueImage, I would have said that "...my backup consisted of 7,258 megabytes..." (MY way of rounding off). I guess, fearful of confusing things more, that I prefer "true numbers" but in spite of that I tend to round off somewhat. Whew, I think I'll quit for now and go take my morning shower <img src=/S/grin.gif border=0 alt=grin width=15 height=15>...

[AlanMiller]

John

I mentioned the anomoly of the lower case "k" at the bottom of my post. I suspect it originates from the fact that the kilogram is actually a base SI unit - not the gram, which might seem more logical. Like the metre and the second, this base unit is all lower case, hence "kilogram".

Prefixes like deci, deka, hecto are not approved SI prefixes and are therefore not the subject of the those (or any?) standards. SI units are prefixed only by intergal powers of 10

[JohnGray]

Alan

> SI units are prefixed only by integral powers of 10

[AlanMiller]

John

<big>I</big> am the Australian reference you seek. <img src=/S/grin.gif border=0 alt=grin width=15 height=15> But perhaps I stand corrected (I'm not convinced yet though). I know that the recommended usage in science/ engineering contexts is as I said. Perhaps this does differ from SI standards... but the jury's still out. <img src=/S/thinks.gif border=0 alt=thinks width=15 height=15>

Alan

[JohnGray]

Alan

I would have thought the national standards institutions in the three major countries of the world would have been good enough for you!

I agree that the hecto, deka and deci prefixes are not strongly recommended, but they still appear in the tables...

John

[diegol]

<img src=/S/yikes.gif border=0 alt=yikes width=15 height=15> And I thought I was confused!!! At least it's not just me... <img src=/S/dizzy.gif border=0 alt=dizzy width=15 height=15>

I had a quick glance and Windows uses 1 MB = 1024 KB. So does PowerDesk, and that's what seems most reasonable to me.

Regarding the use of capital or small letters, I think we can complicate things even further: according to what I remember having read sometime, KB stands for kilobyte whereas Kb stands for kilobit. In my (very short) past experience in the telecom industry I found that in technical proposals salespeople / engineers used both acronyms indifferently. If I'm not wrong, the standard transfer rate is kilobits per seconds (Kbps), but these variants appeared daily: kbps, KBps, KBPS.
So if we say the transfer rate is 64 KBPS, in one extreme scenario we'd be talking about 64 x 1,024 x 8 = 524,288 bits; the extreme opposite would be 64 x 1,000 = 64,000 bits.

It would be a nice business practice to take one line to make clear what the notation means (I am aware that this is highly unlikely to happen). Such a pity I'm not in the industry anymore! <img src=/S/smile.gif border=0 alt=smile width=15 height=15>

[JohnGray]

It's rather easier than you think, if you split the two parts up.

"k" is the SI prefix for kilo;
"B" means bytes, and "b" means bits.

So we could have a transfer rate of 64 kbps, or 64 kb/s or, if we could do superscripts properly in the Lounge, the absolutely correct way would be 64 kbs-1 (where the "-1" was superscripted), all of which meaning "64 kilobits per second".

But then again, I've found that some techies don't have a clue how to work out for a 10 Mbps ethernet link, roughly how long it will take to transfer a 1 GB file, bearing in mind contention, and the like! (I always used to get rung up to work it out for them, since one of my fort

[diegol]

I agree -- I was just trying to show the diversity of interpretations that could rise from vague everyday notations. Since there seems not to be a universal consent about which notation should be used (and, as I sated above, in practice I saw all kinds of notations to mean one single thing), it's conceivable that problems may arise. That I remember, these basic definitions were written neither in the proposal itself, nor in the SLA (Service Level Agreement).
Fortunately parties acted in good faith, but again, one can imagine one of the parties trying to take advantage of the ambiguity; or simply misunderstanding what the other meant (your HD example suits both situations, if at another level).

[fburg]

Sorry, Al. I couldn't resist.

So when a product says you need 250 MB of free storage and 256 MB of RAM (although we know the numbers lie), do you call the vendor and ask: "would that be 250x1000x1024 or 250x1000x1000?"

Have you ever seen a product say "you need 2,732,638 bytes of free storage" or something like that? <img src=/S/grin.gif border=0 alt=grin width=15 height=15>

And what happens when the vendor, MS, and the hard disk manufacturer are not in sync? That is, you think you have enough based on what the vendor says and Windows tells you but, when going thru the install, you can't install bcs the hard disk doesn't really have enough room.

really big <img src=/S/grin.gif border=0 alt=grin width=15 height=15>

Fred