how should a program ask for no SI prefix?

[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.