[net.emacs] ^S/^Q

warren (04/14/83)

Forgive me if I am repeating someting, since we have been down for
some time, but one point that might be getting lost to people not
very familiar with this is that there 3 types of terminals with
respect to flow control:

Those that don't need it at all (Very few)

Those that need it when doing certain control sequences (99%)

Those that need it just printing characters at high speed.  (Very few)

Most editors handle the first two just fine, by providing padding,
but the third is a real problem.  I only know of the vt100 and
hp2621B in this category, and generaly advise anyone who asks to
avoid these two, since there are comparable terminals without the
problem available at lower cost.

Mark's comment that ^S/^Q is faster than padding is true only if the
system response is quick enough.  If you have local area networks,
and other baggage between you and your favorite host, you may be
better off with padding, since the flow control will have to ripple
through multiple stages in each direction.

Basically, the mistake that was made in the design of this protocol
was not to provide some means for transparent encapsulation of the
real ^S/^Q keys.  This was shortsighted but understandable when the
terminal manufacturers did it, but unforgivable when operating
system designers did not put some sort of transparency mechnaism
into terminal drivers, and then used the same non-transparent
protocol for other applications, like machine to machine links.

-- 

	Warren Montgomery
	ihnss!warren
	IH x2494