6 Jan
2005
6 Jan
'05
8:43 a.m.
From: "Tom Jennings" <tomj(a)wps.com>
Hi
In the past when I wanted a non-block binary transfer,
I often had some value that I used as an escape character.
I'd choose a low frequency value to improve throughput.
It is simple, If you want to send a command value, you
send the escape character, first. If you just wanted the escape
character, you'd send it twice. For 8 bit data, you
had 255 commands. EOF could be one of those.
It makes a simple protocol that is easy to implement in
code.
Dwight
> "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 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.)