Gerhard Fiedler <[EMAIL PROTECTED]> wrote: ... > > Part of the CP/M compatibility did include the use of / as flag-indicator > > (the use of \r+\n as line ending also comes from CP/M -- in turn, CP/M > > had aped these traits from some DEC minicomputer operating systems). > > At the time, probably pretty good reasons for using the slash as command > line flag indicator.
In DEC's case, the / was an essentially random choice -- nothing particularly stood either for or against it -- and there was no particularly good reason for CP/M to ape it later, either (Unix is even older than CP/M, _and_ ran on HW essentially identical to that used by some of said DEC OS's, yet, having good designers, it "broke" both these points of "compatibility"... yet didn't suffer in the least thereby). The \r+\n choice is different -- it did indeed have a good reason _at the time_ DEC chose it: for OSs without real device drivers (on machines with no power to spare for even the most trivial processing), sending a bunch of lines to a dumb teletype really needed the lines to be terminated by telling the tty both to return-carriage (the \r) AND to advance paper (the \n) -- and the former had to be first because the carriage-return operation was mechanically slower but could occur at the same time as the paper advance. But these issues did not apply by the '70s, when CP/M was born and Unix got its name (from the previous name, briefly used in the late '60s, of UNICS). Whether there's "a good reason" to embed the consequences of these mechanical issues in fileformats and protocols, destined no doubt to survive for many decades to come, 40 years after said issues had become essentially moot, is another issue... but backwards-incompatible changes ARE always hard (and yet, the original designers of successful systems are basically never as ambitious and visionary as to think of the effect their choices of today will have 40 or 80 years down the road -- systems designed with the mindset of thinking many-decades-ahead tend to fail in their struggle against quick-and-dirty ones, as bemoaned but lucidly analyzed in Gabriel's deservedly famous essay on "worse is better", e.g. at <http://www.jwz.org/doc/worse-is-better.html>). > And, as an aside, I'm sure that MS would have sold more of their Xenix if > the market had wanted it. But the market really wanted DOS... Yes, particularly considering the much higher HW demands of Xenix's entry point, compared to DOS's -- not only did Xenix always require a hard disk, but, for over 2 years, Xenix supported only Zilog Z8001 and later Motorola 68000... it took SCO, in late 1983, to release an 8086 version, and by that time DOS was well entrenched in the marketplace, also supporting floppy-only machines that remained a much more affordable entry point than hard-disk ones for further years. Basically, by the time PCs with hard disks were starting to become widespread, MS had lost interest in marketing Xenix, which only SCO was pushing, so it made sense in '87 for MS to sell SCO Xenix outright in exchange for a large slice of SCO's stock (20%, if I remember right). Alex -- http://mail.python.org/mailman/listinfo/python-list
