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.

-- 
Clive D.W. Feather     | Santa Cruz Operation    | If you lie to the compiler,
clive@sco.com          | Croxley Centre          | it will get its revenge.
Phone: +44 1923 813541 | Hatters Lane, Watford   |   - Henry Spencer
Fax:   +44 1923 813818 | WD1 8YN, United Kingdom | <== NOTE: NEW FAX NUMBER


This page was last changed on Mar 03 1995, 12:19 by mfx@pobox.com. Comments and corrections welcome.