by Michael S. Kaplan, published on 2008/06/09 10:01 -04:00, original URI: http://blogs.msdn.com/b/michkap/archive/2008/06/09/8583404.aspx
The question from a friend was straightforward enough (name withheld to avoid unnecessary embarrassment!):
ASCIIS don’t have half width versions, do they? Are the full/width distinction also only applicable to Japanese characters?
I was momentarily confused at what she meant, and then I realized.
She was thinking of the Katakana subrange (U+30a0 - U+30ff) and the chunk of the this subrange containing halfwidth Katakana (U+ff65 - U+ff9f).
And then after looking at the chunk of the this subrange containing fullwidth ASCII (U+ff01 - U+ff5e), she was just wondering if there was a special halfwidth ASCII subrange.
Technically there is, though its name of the containing range can perhaps make finding it more difficult if one has ASCII in one's mind.
So we can probably excuse for this momentary lapse that caused her to mentally think of the ASCII as fullwidth and some unknown compatibility range to contain the halfwidth (described in her own words as a "total mental gap").
The hint comes from the name of the subrange containing both the fullwidth Latin and the halfwidth Katakana (Halfwidth and Fullwidth Forms).
The name is Basic Latin. :-)
As a somewhat separate issue, I have talked about how these "width" issues are (by convention) distinguished today, in posts like this one and this one and this one (among others).
And in the end I find her "total mental gap" to be quite forgivable -- it is quite easy to see patterns and without giving it too much though expecting the patterns to be seen consistently elsewhere. The random and inconsistent nature of patterns in Unicode (and innocent people not expecting to be tripped up by them) is just the way things are....
This blog brought to you by ゴ (U+30b4, aka [FULLWIDTH ]KATAKANA LETTER GO)