Subject: bug#8479: 24.0.50; Strange error message upon M-z M-z

From: Kevin Rodgers <[email-masked]>
Date: Wed, 13 Apr 2011 20:05:40 -0600

On 4/12/11 12:00 AM, Eli Zaretskii wrote:
>> From: Kevin Rodgers<[email-masked]>
>> Date: Mon, 11 Apr 2011 23:15:50 -0600
>>
>> Yes, but why is M-z not a character?
>
> Because the "M-" part sets bits in the area outside the valid range of
> character code points.

This is what I was looking for, in the Meta-Character Syntax section of the
Emacs Lisp manual:

A "meta character" is a character typed with the <META> modifier key.
The integer that represents such a character has the 2**27 bit set.  We
use high bits for this and other modifiers to make possible a wide
range of basic character codes.

    In a string, the 2**7 bit attached to an ASCII character indicates a
meta character; thus, the meta characters that can fit in a string have
codes in the range from 128 to 255, and are the meta versions of the
ordinary ASCII characters.  *Note Strings of Events::, for details
about <META>-handling in strings.

-- 
Kevin Rodgers
Denver, Colorado, USA