Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!decvax!ittvax!dcdwest!sdcsvax!sdcrdcf!hplabs!sri-unix!mab@AIDS-UNIX.ARPA From: mab@AIDS-UNIX.ARPA Newsgroups: net.unix-wizards Subject: Re: VT100 and bagbiting Message-ID: <1329@sri-arpa.UUCP> Date: Wed, 27-Jun-84 10:34:53 EDT Article-I.D.: sri-arpa.1329 Posted: Wed Jun 27 10:34:53 1984 Date-Received: Sat, 30-Jun-84 05:41:20 EDT Lines: 31 From: Mike Brzustowicz 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