MRAB schreef:
On 2012-10-14 23:38, Dave Angel wrote:
On 10/14/2012 08:48 AM, Roy Smith wrote:
In article <507a3365$0$6574$c3e8da3$54964...@news.astraweb.com>,
Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info> wrote:
Remember using PEEK and POKE commands with BASIC back in
1978? Pretty much impossible in Python.
But, trivial to implement as an extension :-)
PEEK and POKE were intended to be used with memory mapped devices.
Simplest example is the 6502 chip, which had no I/O bus -- it was all
memory mapped. Want to change baud rate? poke a byte somewhere.
These days, the only device I can think of that's usually memory mapped
is the video. And few programs talk to it that way.
Now, INP and OUT (or various similar names) were for doing port I/o.
But I suspect that modern systems aren't going to let you do much of
that either.
It depends on the CPU. Some have specialised instructions for I/O,
others don't.
I think Roy Smith meant that the OS on modern systems generally prevents
direct access from user space to either memory mapped I/O or port mapped
I/O. Embedded systems might allow direct access, but AFAIK Python
doesn't run on those.
Best regards,
Roel
--
"Too often we hold fast to the cliches of our forebears. We subject all
facts to a prefabricated set of interpretations. Too often we enjoy the
comfort of opinion without the discomfort of thought."
-- John F Kennedy
r...@roelschroeven.net
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