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Re: about meta character and character coding .
From: |
Colin S. Miller |
Subject: |
Re: about meta character and character coding . |
Date: |
Thu, 06 Aug 2009 11:37:22 +0100 |
User-agent: |
Mozilla-Thunderbird 2.0.0.22 (X11/20090706) |
waterloo wrote:
I can not understand the following para in Emacs Lisp Reference :
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. (In Emacs versions 18 and older, this
convention was used for characters outside of strings as well.)
One bit has two states.
Does 2**7 bit denote 7 bits ?
It means the 7th bit (counting from 0),
which has the value 128, or 2 to the power of 7.
(the caret character, which is sometime used to represent powerof,
also means the bitwise-or operation in the C programming language).
What does `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. ' mean ?
It means the character A has value 65, and meta-A has the value 193,
being 128+65.
Thanks
HTH,
Colin S. Miller
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