From: Ullrich von Bassewitz (uz_at_musoftware.de)
Date: 2003-05-17 12:59:25
Hi!
On Tue, May 13, 2003 at 05:30:10PM -0600, Justin England wrote:
> It looks like all keyboard entry has the high bit set.
I have to admit that this seems very confusing to me. It looks like bit 7 is
definitely needed for screen I/O (cputc will always set it before writing a
character to the screen). The existing routine for keyboard input (cgetc) sets
bit 7 if OpenApple is down, or better: it clears bit 7 if open apple is up.
However, one important reason (if not the only one), why characters read from
the keyboard have bit 7 set is that this is the key strobe, that is, the
hardware signal that tells if a new key is available.
I'm not sure what consequences to draw from this information. It seems that C
programs work as they are (maybe with the exception of the character
classification routines). Assembler programs work depending on the pogrammers
assumptions. Currently I think it would be the best "solution" to leave
anything as it is. Or is there something I've overlooked?
Regards
Uz
--
Ullrich von Bassewitz uz_at_musoftware.de
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This archive was generated by hypermail 2.1.3 : 2003-05-17 13:00:27 CEST