VT100 and bagbiting

[mab at AIDS-UNIX.ARPA]

From:  Mike Brzustowicz <mab at AIDS-UNIX.ARPA>

About DC3/DC1, since they were intended to be sent by the COMPUTER to
control devices on the TERMINAL, I don't see how "it is fairly easy to see
how the DC3/DC1 flow control protocol logically evolved from this."  The new
way, although it may be a de facto industry standard, is backwards from the
intended use of the codes (that is, having the TERMINAL cantrol flow from
the COMPUTER is backwards).  Historically, I believe this started as a stop
gap measure so that the USER could stop the COMPUTER when too much
information was arriving at once, and noone had MORE or anything like it.
Now manufacturers are using it so that they can claim a higher baud rate for
their terminals than the terminals are *really* capable of.  There are a
number of reasonably priced terminals that can work at high speeds, do all
the nifty stuff and not require flow control or padding, so it can be done.
I believe it to be a marketing ploy, and a technically poor decision, but
one that, alas, those that can't pick their own terminals or machine may be
stuck with.

As for ESC, I believe you'll find that the use of escape for programming
escape sequences (as in EMACS) predates ANSI X3.64.  In ANSI X3.4 (ASCII),
ESC was a prefix for transmitting "out of band" characters or sequences,
which is its approximate use in EMACS.  (In EMACS, it is actually
prefix-META, that is, make the next character a meta character, for
terminals that don't support meta chartacters, and most don't.  Many EMACS
versions allow one to redefine prefix meta to be some other character.  Some
will interpret the eighth bit of 8 bit ASCII as the meta bit.) Besides, in
X3.64, aren't the overwhelming majority (like all but one, or maybe two) of
escape sequences defined as, again, controlling the TERMINAL from the
COMPUTER?

-Mike