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From: karl@osu-eddie.UUCP
Newsgroups: comp.emacs
Subject: Re: What's wrong with flow control?
Message-ID: <2660@osu-eddie.UUCP>
Date: Thu, 27-Nov-86 11:21:07 EST
Article-I.D.: osu-eddi.2660
Posted: Thu Nov 27 11:21:07 1986
Date-Received: Fri, 28-Nov-86 01:50:08 EST
References: <3910001@nucsrl.UUCP>
Organization: OSU
Lines: 30

gore@nucsrl.UUCP writes:
>In one of the installation documentation files for GNU Emacs, Richard Stallman
>expresses his displeasure (to put it mildly) with the way DEC's terminals use
>control-S and control-Q (XON/XOFF) for flow control.  He says its a
>"brain-damaged" design.
>
>Could somebody tell me why that is the case?  If that is the case?  What would
>be a better synchronization method?  The only decent method I can think of
>would use hardware handshaking...

That's what CTS & RTS (clear-to-send and request-to-send) are for:
hardware handshaking.  And if UNIX tty drivers and related hardware
were set up to do it properly, that would be the way to go.
Otherwise, the solutions are either to make a terminal for which
padding can be sufficiently easily specified, so that you basically
trust the terminal not to get behind and screw up; or just make a
terminal whose firmware is faster than its fastest data rate.  (Don't
laugh, it's not that difficult.  It's a poor commentary on DEC et al
that they can't do so themselves.)

As it is, making ^S/^Q into flow-control chars forces them into being
an awful special case.  If people aren't to type ^S or ^Q, why is ^U
acceptable?  Or ^Z?  Or ^C?  Or any of those other characters people
have learned to love on their ASCII terminals?

While I sometimes disagree with the (perhaps caustic) view taken by
Richard toward ^S/^Q, I have to agree with the basic position: it's a
bad design.
-- 
Karl