Newsgroups: comp.std.internat From: clive@sco.com (Clive D.W. Feather) Subject: Re: Definitions of SP, NBSP, and SHY in ISO 8859 (and 10646?) Organization: Santa Cruz Operation Ltd., Watford, United Kingdom Date: 03 Mar 1995 04:52:33 MET In article <1995Mar2.222402.12550@admin.kth.se>, Olle Jarnefors <ojarnef@admin.kth.se> wrote: > 0020 SPACE > 2000 EN QUAD > 2001 EM QUAD > 2002 EN SPACE > 2003 EM SPACE > 2004 THREE-PER-EM SPACE > 2005 FOUR-PER-EM SPACE > 2006 SIX-PER-EM SPACE > 2007 FIGURE SPACE > 2008 PUNCTUATION SPACE > 2009 THIN SPACE > 200A HAIR SPACE > For the other spacing characters 2000-200A I expect there > can be given definitions of the type: > -- to represent an amount of unfilled space between the > surrounding characters normally corresponding to the width of x > where x for 2003 EM SPACE, for example, could be "a LATIN CAPITAL > LETTER M in the current font". > I'm not very knowledgeable about typographical matters so I > can't propose good width measures for the different > typographical space characters of UCS.Well, many years ago I used to work with real lead type (letterpress type). With this, an em space was a square bit of type. An en space is half a square - it's the normal interword spacing.
Suppose you are setting 12 point type (the height of each piece of lead) with 2 point leading (the thickness of the lead strips between the rows of type). Then the baselines of characters would be 14 points apart. An em space is a square, so it's 12 points wide. An en space is half that: 6 points wide. A 3-per-em, 4-per-em, and 6-per-em space are 4, 3, and 2 points wide respectively. In 18 point type they would be 18, 9, 6, 4.5, and 3 points respectively.
A thin space was a strip of postcard, and a hair space a strip of paper; neither had a formal definition. They were used for fine-tuning.
A figure space is a space as wide as a digit, assuming all digits have the same width. In many typefaces all digits are exactly 1 en wide, so an en space did duty as a figure space. I don't know about punctuation space, but perhaps it's the same thickness as a full stop or colon.
Em quad and en quad should be a filled-in square and half-square, not a space, if I recall correctly.
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