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From: gnu@hoptoad.uucp (John Gilmore)
Newsgroups: net.bugs.4bsd,net.info-terms
Subject: Re: Using "am" or "xn" in programs considered harmful
Message-ID: <958@hoptoad.uucp>
Date: Fri, 8-Aug-86 06:33:32 EDT
Article-I.D.: hoptoad.958
Posted: Fri Aug  8 06:33:32 1986
Date-Received: Sat, 9-Aug-86 07:02:46 EDT
References: <3864@utah-cs.UUCP> <925@hoptoad.uucp> <2753@mit-eddie.MIT.EDU>
Organization: Nebula Consultants in San Francisco
Lines: 27
Xref: watmath net.bugs.4bsd:2270 net.info-terms:1050

Aha!  The problem is coming out!

Some people (Doug Gwyn for example) think "am" means this:

	am:xn@	terminal moves to next line after col 80
	am:xn:	terminal moves to next line after col 80 but ignores next NL
	am@	Can't depend on what terminal does in col 80

On the other hand, Barry Margolin points out that "Applications need to
know whether they can safely output to [column 80 of the last line]
without causing the screen to scroll."  The above definitions provide
no guidance about this; so some software appears to be assuming:

	am@	terminal stays in col 80 after printing char there

This is the problem I've been facing.

So, let me modify my suggestion.  If "am" is set, you can assume that
the cursor will move to the next line.  If "am" is not set, **you must
not assume anything**.  In either case, you can't safely write to column
80 of the last line.

This would mean that removing "am" from a termcap entry would never
cause it to fail.  That is what I am after.
-- 
John Gilmore  {sun,ptsfa,lll-crg,ihnp4}!hoptoad!gnu   jgilmore@lll-crg.arpa
		     May the Source be with you!