Detecting multiple keypresses

[kstahl]

Howdy,

I would like to get down to the nitty-gritty of the keyboard's operation.
Specifically, I would like to poll only a few keys on the keyboard, and I
would like to know when more than one key is pressed. In other words, I
would like to know how to access the keyboard's scan lines, so that if, for
example, the user is holding two of the arrow keys pressed simultaneously, I
will get a continuously changing response of Left-Right-Left-Right-and so
on. So far, all that comes to mind is scanf(), but this is clearly
inadequate.

Thanks for your help,
-Karl

[Joona I Palaste]

Re: Detecting multiple keypresses

kstahl <kstahl@stanfor d.edu> scribbled the following:[color=blue]
> Howdy,[/color]
[color=blue]
> I would like to get down to the nitty-gritty of the keyboard's
> operation.[/color]

Can't be done in ISO standard C. Strictly speaking, you can't read the
keyboard at all in ISO standard C, merely the standard input stream.
Fortunately, most of the time there is a console handler reading the
keyboard and feeding the characters to the standard input stream. How it
does that is off-topic for comp.lang.c.

--
/-- Joona Palaste (palaste@cc.hel sinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"Remember: There are only three kinds of people - those who can count and those
who can't."
- Vampyra

[kstahl]

Re: Detecting multiple keypresses

Thanks for your prompt response. I'm not familiar with "console handlers" -
can you recommend a newgroup/website where I might learn more about such
topics?


"Joona I Palaste" <palaste@cc.hel sinki.fi> wrote in message
news:c7tsvt$hd9 $1@oravannahka. helsinki.fi...[color=blue]
> kstahl <kstahl@stanfor d.edu> scribbled the following:[color=green]
> > Howdy,[/color]
>[color=green]
> > I would like to get down to the nitty-gritty of the keyboard's
> > operation.[/color]
>
> Can't be done in ISO standard C. Strictly speaking, you can't read the
> keyboard at all in ISO standard C, merely the standard input stream.
> Fortunately, most of the time there is a console handler reading the
> keyboard and feeding the characters to the standard input stream. How it
> does that is off-topic for comp.lang.c.
>
> --
> /-- Joona Palaste (palaste@cc.hel sinki.fi) ------------- Finland --------\
> \-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
> "Remember: There are only three kinds of people - those who can count and[/color]
those[color=blue]
> who can't."
> - Vampyra[/color]

[Joona I Palaste]

Re: Detecting multiple keypresses

kstahl <kstahl@stanfor d.edu> scribbled the following:[color=blue]
> Thanks for your prompt response. I'm not familiar with "console handlers" -
> can you recommend a newgroup/website where I might learn more about such
> topics?[/color]

It depends on what operating system you are using. Here are a few
suggestions.
For MS Windows: comp.os.ms-windows.program mer
For Unix/Linux: comp.unix.progr ammer

--
/-- Joona Palaste (palaste@cc.hel sinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"To doo bee doo bee doo."
- Frank Sinatra

[Neil Kurzman]

Re: Detecting multiple keypresses

oona I Palaste wrote:
[color=blue]
> kstahl <kstahl@stanfor d.edu> scribbled the following:[color=green]
> > Howdy,[/color]
>[color=green]
> > I would like to get down to the nitty-gritty of the keyboard's
> > operation.[/color]
>
> Can't be done in ISO standard C. Strictly speaking, you can't read the
> keyboard at all in ISO standard C, merely the standard input stream.
> Fortunately, most of the time there is a console handler reading the
> keyboard and feeding the characters to the standard input stream. How it
> does that is off-topic for comp.lang.c.
>
> --
> /-- Joona Palaste (palaste@cc.hel sinki.fi) ------------- Finland --------\
> \-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
> "Remember: There are only three kinds of people - those who can count and those
> who can't."
> - Vampyra[/color]

With PC hardware it is not possible. getch() will give you a Key and scan code.
There is no held down status.

[Thomas Matthews]

Re: Detecting multiple keypresses

Neil Kurzman wrote:[color=blue]
> oona I Palaste wrote:
>
>[color=green]
>>kstahl <kstahl@stanfor d.edu> scribbled the following:
>>[color=darkred]
>>>Howdy,[/color]
>>[color=darkred]
>>>I would like to get down to the nitty-gritty of the keyboard's
>>>operation.[/color]
>>
>>Can't be done in ISO standard C. Strictly speaking, you can't read the
>>keyboard at all in ISO standard C, merely the standard input stream.
>>Fortunately , most of the time there is a console handler reading the
>>keyboard and feeding the characters to the standard input stream. How it
>>does that is off-topic for comp.lang.c.
>>
>>--
>>/-- Joona Palaste (palaste@cc.hel sinki.fi) ------------- Finland --------\
>>\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
>>"Remember: There are only three kinds of people - those who can count and those
>>who can't."
>> - Vampyra[/color]
>
>
> With PC hardware it is not possible. getch() will give you a Key and scan code.
> There is no held down status.
>
>
>[/color]

Then how does Windows obtain the data for its key press messages?
Last time I looked, the Windows operating system could differentiate
between when a key was pressed and released.

--
Thomas Matthews

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Other sites:
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[Dan Pop]

[OT] Re: Detecting multiple keypresses

In <LXLoc.2401$kM5 .1192@newssvr16 .news.prodigy.c om> Thomas Matthews <Thomas_Matthew sSpitsOnSpamBot s@sbcglobal.net > writes:
[color=blue]
>Then how does Windows obtain the data for its key press messages?
>Last time I looked, the Windows operating system could differentiate
>between when a key was pressed and released.[/color]

IIRC (back in my MSDOS days I used to play with the keyboard interface of
the PC, but it's been 15 years ago...) the keyboard is "seen" as an 8-bit
port at some I/O address that "remembers" the last event received from
the keyboard. 7 bits are used for the scan code and 1 bit to indicate
whether the key was pressed or released.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

[Alan Balmer]

Re: Detecting multiple keypresses

On Thu, 13 May 2004 14:51:23 GMT, Thomas Matthews
<Thomas_Matthew sSpitsOnSpamBot s@sbcglobal.net > wrote:
[color=blue]
>
>Then how does Windows obtain the data for its key press messages?
>Last time I looked, the Windows operating system could differentiate
>between when a key was pressed and released.
>[/color]
There are separate scan codes for key down and key up. However, it's
*still* not topical here - take the discussion to some place like
comp.os.ms-windows.program mer, where the answers will be more
plentiful and more accurate.

--
Al Balmer
Balmer Consulting
removebalmercon sultingthis@att .net