21 Apr
2010
21 Apr
'10
10:05 a.m.
On 21 Apr 2010 at 7:49, allison wrote:
By null I meant if you read RDR: or wrote to PUN: the
data would go
to the bit bucket and not to any device.
Exactly so. If you have, for example, an Amstrad Joyce, there's
nowhere to send or receive the data, as there is no (standard) extra
port. There's a printer, but that's a horse of a different color and
not serial at all.
But I've also seem (and been guilty of one or two) CP/M
implementations that completely ignore implementing IOBYTE, so that
any attempt at redirection using STAT fails. If all you have is a
memory-mapped console display and integrated keyboard and printer,
IOBYTE makes little sense for most applications. I suppose one could
implicitly redirect RDR to the keyboard, again, it makes little
sense.
PIP has a couple of device names that most CP/M implementations are
meaningless (INP: and OUT:) and many others (e.g. UC1:, CRT:) that
are known only to PIP.
--Chuck