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From: raymond@math.berkeley.edu (Raymond Chen)
Newsgroups: comp.lang.c
Subject: Re: NOVICE question: How to know when a key is pressed
Keywords: key, keypress, c, novice
Message-ID: <1991Apr12.230400.12749@agate.berkeley.edu>
Date: 12 Apr 91 23:04:00 GMT
References: <1991Apr11.155200.12819@ericsson.se>
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Reply-To: raymond@math.berkeley.edu (Raymond Chen)
Organization: U.C. Berkeley
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In-Reply-To: etxpihl@tore.ericsson.se (DEE Tomas Pihl)
Originator: raymond@sunkist.berkeley.edu

In article <1991Apr11.155200.12819@ericsson.se>, etxpihl@tore (DEE Tomas Pihl) writes:
>I want to know how you can scan if a specific key has been pressed. ...

You didn't say what operating system you were using, so I'll assume you're
using what I'm using.

The keyboard strobe lives at $C000; when a key is available, the top bit
goes on.  The lower seven bits contain the ASCII code of the key that was
pressed.  To clear the strobe, access memory location $C010.  Note also
that if the high bit of $C062 is clear, you should convert uppercase ASCII
characters to lowercase; this is the standard method for entering lowercase
for those who have installed the `shift key mod' by connecting the BUTTON2
pin on the game controller chip to the second connector pin on the keyboard
decoder card.  (Only works for newer keyboards; for older ones, you'll need
to do some soldering.)

Hope this helps.
--
This article has not been closed-captioned for the humor-impaired.
[Easy extra credit:  What computer system am I describing?]