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From: roy@phri.UUCP (Roy Smith)
Newsgroups: comp.emacs
Subject: Re: What's wrong with flow control?
Message-ID: <2518@phri.UUCP>
Date: Sun, 30-Nov-86 19:49:00 EST
Article-I.D.: phri.2518
Posted: Sun Nov 30 19:49:00 1986
Date-Received: Sun, 30-Nov-86 23:35:03 EST
References: <3910001@nucsrl.UUCP> <388@viper.UUCP>
Reply-To: roy@phri.UUCP (Roy Smith)
Organization: Public Health Research Inst. (NY, NY)
Lines: 24

In article <388@viper.UUCP> ddb@viper.UUCP (David Dyer-Bennet) writes:
> A positive system, on the other hand, works by saying "You may now send
> me up to 15 characters".  You do so.  Nobody has to jump around trying
> to avoid timing windows.

	Two problems with this.  The first is that it adds extra overhead,
and makes the protocol more complicated to boot.  It can reasonably be
argued that with 9600 baud lines it doesn't much matter if you burn a few
extra characters per line of output.  It can also be reasonably argued that
with smart serial line controllers and smart terminals, most of this added
complexity can be hidden from the user.

	The second problem is harder to get around.  Let's say you tell me
that it's OK to send 15 characters now.  Does that mean 15 graphic (i.e.
printable) characters, or can it include a "run confidence test" escape
sequence which could take 5 minutes to complete?  That may be an extreme
example, but consider than even a simple NL/CR with smooth-scroll turned on
may take a good fraction of a second.
-- 
Roy Smith, {allegra,cmcl2,philabs}!phri!roy
System Administrator, Public Health Research Institute
455 First Avenue, New York, NY 10016

"you can't spell deoxyribonucleic without unix!"