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From: jaap@mcvax.UUCP (Jaap Akkerhuis)
Newsgroups: net.text
Subject: Re: Who uses points?
Message-ID: <991@mcvax.UUCP>
Date: Thu, 20-Mar-86 19:52:50 EST
Article-I.D.: mcvax.991
Posted: Thu Mar 20 19:52:50 1986
Date-Received: Sat, 22-Mar-86 22:23:32 EST
References: <130@cs.qmc.ac.uk>
Reply-To: jaap@mcvax.UUCP (Jaap Akkerhuis)
Organization: CWI, Amsterdam
Lines: 27

In article <130@cs.qmc.ac.uk> liam@cs.qmc.AC.UK (William Roberts) writes:
 > The PostScript manual says that a printers' point is 1/72 of an
 > inch (or possibly 1/72.27 of an inch).  Does this mean that
 > points are a UK/US unit only, or do printers everywhere use
 > them?  Where does the 72.27 come from?

In the UK/US the most used point system is the "Pica points". The officially
value of a 72 point (or 12 Pica) in this system is 1 inch (and something
small). But note that the exact size of a point can be dependent on the brand
of the typesetter manufacturer, the traditional value actually used in the
printer shop you ask about the size of point, or a combination of the two.

In other places of the world (France, Holland etc.) the traditional value of a
point comes from the Didot system. The size is different. 1 Pica point is
about 0.934572 times a Didot point. And of course the note about manufacturers
and printer shop is valid as well.

This reminded me that when out typesetter arrived it was using Didot points,
so everything came out too big (using troff). The typesetter was made in the
USA, and I was sure, it was not an error in my C/A/T simulating filter.
After some digging (thanks Piet) in the diagrams we found a switch to
make it Pica points. As far as I can remember (and I don't have the diagrams
always at home so cannot check) it changed a reference voltage for some DAC's
int the X & Y deflection circuits. I think there is even a ten turn pot so you
can adjust the point to the above mentioned standard of the printing shop.

	jaap