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From: warren@ihwpt.UUCP (warren montgomery)
Newsgroups: comp.emacs
Subject: Re: What's wrong with flow control?
Message-ID: <1273@ihwpt.UUCP>
Date: Mon, 1-Dec-86 09:35:47 EST
Article-I.D.: ihwpt.1273
Posted: Mon Dec  1 09:35:47 1986
Date-Received: Tue, 2-Dec-86 02:30:07 EST
References: <3910001@nucsrl.UUCP> <2660@osu-eddie.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 24

Others have covered most of the problems with the ^S/^Q flow control
scheme.  I would like to add one more place where the implementers
of this scheme made what I feel is a serious mistake:  The protocol
provides no escape mechanism to allow one end to tell the other that
"this ^S is for real, not for flow control".  All of the other
special characters in unix can be escaped in order to pass through. 
If the same rules had been applied to ^S and ^Q, then a smart
terminal could be programmed to generate \^S and \^Q on function
keys or even on the keyboard in some cases, while using ^S/^Q for
flow control elsewhere.  

The place this lack really shows up is in "cu", and similar
unix-to-unix connection programs, which frequently wind up needing
^S/^Q flow control but provide no mechanism for passing ^S and ^Q
through transparently.  With most or all of the emacs
implementations around you can work around the problem through
special control character prefixes, remapping the keyboard, and
similar mechanisms, but it still is the number one source of user
trouble reports for me, because working around the trouble is
tricky.

-- 

Warren Montgomery,  ihesa!warren