Importing binary files without removable storage nor non-bundled

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Thu Jan 6 18:09:35 2005

>
> >> "Binary reads from a device are not
> >> allowed" is the message at 8753 in DR-DOS 3.41.
>
> On Wed, 5 Jan 2005, Vintage Computer Festival wrote:
>
> > The question I haven't seen answered yet is, "Well, why the hell not???"
>
> The real answer is: there is no out-of-band signalling, so one of

The obvious out-of-band signal is a keypress (either the 'Any key' or
some partciular one like ctrl-C). In other words, COPY /B should copy all
characters from the serial port to the file _without modification_ until
there's a keypress. The user has to start the copy, get the other device
to start sending data, then press a key when it's finished.

> the 128 in-band symbols (SUB, 26 decimal) is chosen to mean "END
> OF FILE". It's borrowed from CP/M-80; I don't know where DR got
> it; it seems un-DEC-ish.
>
> ("Out of band" signalling is, for RS-232 et al, the hardware
> handshake lines. No one likes them, everyone complains like
> babies, so they have essentially been deprecated.)

That's mainly because they are not hardware handshake lines, at least not
for things like that. They were status lines between a terminal and the
local modem, not the device at the other end of the link. Using them for
flow cotnrol is actually contrary to the RS232 standard (or at least the
one I saw).

I suppose using the for end-of-file (which could be taken to be similar
to loss-of-carrier or something) would sort-of comply with the standards,
but I doubt that was ever done.

Problem is that if you use them as they were originally intended then
you'll have problems because nobody else does that. I remember bitterly
doing battle with the HP82164 RS232 interface. This seems to have been
designed by someboy who has read the standard but has never seen a
real-world 'RS232' device. I seem to remember some very odd pin-swaps to
get it working...

-tony
Received on Thu Jan 06 2005 - 18:09:35 GMT