Terminal output: parity, 7 vs. 8 bits, etc.

[Mark Horton]

With reference to rewriting the tty driver:

The tty driver HAS BEEN rewritten.  USG did it in System III.  Most
people's initial reaction was "My God, I'm going to have to rewrite
all my software because it's incompatible!"  However, in the 3 years
or so since it's been out, people are beginning to appreciate the
orthogonality it presents.  You can control most of the hardware bits
(parity, character size, etc) independently.  (The one thing you can't
do is have different input and output baud rates, but this feature only
seems to be used at places like Stanford for 1200 baud output with 150
baud input - such modems apparently cost less than real 1200 baud modems.)
Of course, none of the wonderful Berkeley features (crterase, ctlecho,
job control, word erase, line retype, etc) are present in the USG driver,
although the echoe bit is a kludged approximation to crterase.

Of course, this dichotomy of tty drivers (USG vs Berkeley) is the single
most frustrating cause of incompatibility between System V and 4BSD.

My general feeling now is that the ideal tty driver would be the USG tty
driver with the Berkeley extensions added.  I think Berkeley feels this
way too.  The reason that 4.2BSD does not have a USG-compatible tty driver
in it is that BERKELEY IS NOT LEGALLY ALLOWED TO DO SO.  You see, 4.2BSD
is based on UNIX/32V, which costs $300 to universities.  System III costs
$3000 to universities, and the improvements from V7 to System III are few
enough and unimportant enough that it just doesn't seem worth it.  If
Berkeley includes anything from System III in 4BSD, they must require that
anyone who gets 4BSD buys the more expensive USG license.  The System III
manual is apparently not in the public domain, either, like the V7 manual is.

This situation is gradually improving.  System V has a more reasonable price
tag on it, and is being aggressively pushed by AT&T as a standard.  The
next 4.nBSD will probably require a System V license.  So the legal problems
are going away.  It might be nice if someone would port the System V tty
driver to 4.2BSD, putting the 4BSD extensions back in, and give it to
Berkeley.  (Some upward compatibility code would be crucial as well.)
I can't speak for Berkeley, but I believe they would be interested.