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Why doesn't Python include non-blocking keyboard input function?

Chris Angelico rosuav at gmail.com
Fri Oct 28 13:55:57 EDT 2016 
On Sat, Oct 29, 2016 at 4:50 AM, Terry Reedy <tjreedy at udel.edu> wrote:
> On 10/28/2016 11:03 AM, Chris Angelico wrote:
>>
>> On Sat, Oct 29, 2016 at 1:54 AM, Dennis Lee Bieber
>> <wlfraed at ix.netcom.com> wrote:
>>>
>>> https://en.wikibooks.org/wiki/QBasic/Advanced_Input
>>> indicates that INKEY$ doesn't even test the keyboard for presses, but is
>>> only retrieving the next item from the keyboard input /buffer/ (which
>>> that
>>> article goes on to mention used to be part of a dedicated hardware chip,
>>> but now is a software/interrupt maintained buffer).
>>
>>
>> True, but in practice, it's the same thing. The keyboard buffer ring
>> gets populated by the interrupt handler, and INKEY$ looks at the
>> buffer, sees if it's empty (return ""), and if not, consumes and
>> returns one key.
>
>
> 'ring bugger' implies a finite limit tot he size of the queue.  Do either of
> you know what it is?
>

16 slots, each 16 bits (8 bits character, 8 bits scan code). I think
it filled at 15, though, from memory; if the head and tail pointers
are equal, the buffer is empty, ergo the buffer cannot completely
fill. That's where the classic "bip" of keyboard-buffer-full came
from.

ChrisA
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