how should a program ask for no SI prefix?

[StephenG1CMZ]

With SI written units, the absence of an SI prefix is indicated by a null: as in "m" instead of "mm".

I may have missed it (I have only looked at free specs) but I have not seen an equivalent that would suit a program.

If I have a pop-up selector (CHOOSE or INPUT) prompting for K,M,G,... how should I signify " no prefix"? Which will probably be the default.
The problem with "no prefix" is:
- its longer than K, so might not fit your form
- it needs translation
- The opposite of "no prefix" is "a prefix", not a specific one.

Using a null entry (equivalent to the written " m" for metres) is inconvenient, particularly on the HP Prime: There is no clue that this is your prefix input rather than something else, and HP Prime's default prompt is for a value - the inexperienced user is likely to try to type in a number rather than select a choice.

For mathematical users one might avoid translation by using a number but even this can be confusing. Should one specify " 1" as in multiply by 1,1000,1000000? Or should one specify ^0 as in 1e6,1e3,1e0? Of course either could be used - but are there any hints as to what works and what doesn't? Does the SI organisation have any recommendations? (And if not, why not?)

[walter b]

Why not use a blank character? Just crossed my mind...

d:-?

[StephenG1CMZ]

(11-24-2015 03:37 PM)walter b Wrote:  Why not use a blank character? Just crossed my mind...

d:-?

Perhaps I am being too fussy...

The only difficulty is that you do not see "no prefix" or "please enter a prefix" as a default entry, you just see a blank (in the case of an INPUT). So it is not immediately obvious that the user should click on it and select K or M. suppose your input form has a second box: " ", " clockwise", "anti-clockwise". Which one are you at?
On the Prime the default prompt is "Enter a value for ..."... I have seen some novices try to type in 1000.
Of course having helpful text helps avoid that, but that means more translations.

I am almost tempted by " SI", but in some cases I will want to use the computing equivalents to SI instead (1024 instead of 1000 for K).

I suspect there is no perfect answer - but I am a little surprised no-one has proposed a standard recommended method.

[walter b]

Hmmh, still not sure I understand what you want. Let me try it this way:

If you present something like a dropdown menu letting the user choose a prefix then I'd suggest P/T/G/M/k/ /m/µ/n/p/f if this would cover the needs (watch the lower case k!). If a blank character is forbidden for any reason whatsoever I'd suggest printing "none" as an alternative.

HTH a bit

d:-?

[renif]

The SI rules do not provide any specific denomination for the factor 1, as the unit shall be used without any prefix in this case. However, "none" often is used as an explanatory term in (english) tables of unit prefixes. For typographic convenience a long dash "---" could be used (not language specific). Or something like "1 x ". The result is a unit, either with or without prefix, no space between the two. So, you probably would like to prompt explicitly for the correct unit prefix "SI Prefix" or "IEC 80000-13 Prefix" (for binary values) before the unit symbol, in order to make this composition process clear to an inexperienced user. But, may have missed the issue, too.

[Vtile]

Is the problem m^-1 , 0*m or 1*m ??? I don't get it. There is no prefix for meter(m) since it is meter and basic unit and all others meters are actually meters with only multiplied by 10^x which is just shortened with prefix for convenience, while doing calculation you still need to use 10^x as magnitude fit atleast in your head..

Or is this related to KiB vs kB vs KB vs kb vs Kb argue??
\( k_{2}B \) vs \( k_{10}B \)
There is no such thing at my knowledge as K-prefix in SI system, only small k for kilo (10^3).


Edit. Latex doesn't work hmmpf. I see It relates somehow quick edit vs. full edit.
Edit∞. Ok rereading through who knows how many times this seems indeed relate to KiB vs kB problem I have no solution it is defacto a mess and 99% of times used what ever way one might feel it fits his/her pocket. Look at Kibi https://en.wikipedia.org/wiki/Binary_prefix#kibi This ofcourse doesn't solve the problem. You must write a help popup window for the proper use of it, this is too new thing and too misused so it needs some enlightment to users next 20 years before it starts to be defacto understood thing. Then there is the b vs B a bit vs byte problem.

Edit∞^2 Ki for binary kilo isn't even a good prefix since it still too easily misunderstood to 10 base SI kilo prefix, maybe 20 years from now. Why they didn't propose something like bkB and bMB that clearly shows that wait a bit (heh) there is something odd and not just fancy way to write Kilo. In example I my self believed for years that Ki is only a some L337 H4x0R way of writing kilo, before I found out that it actually means binary kilos.