Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!mit-eddie!bbn!jr@bbn.com
From: jr@bbn.com (John Robinson)
Newsgroups: comp.emacs
Subject: Re: Problem with GNU Emacs.
Summary: C-^, not C-~
Keywords: control characters names
Message-ID: <49650@bbn.COM>
Date: 13 Dec 89 21:01:29 GMT
References: <3071@uceng.UC.EDU> <14572@eerie.acsu.Buffalo.EDU> <1013@dialogic.UUCP>
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Reply-To: jr@bbn.com (John Robinson)
Distribution: usa
Organization: BBN Systems and Technologies Corporation, Cambridge MA
Lines: 39
In-reply-to: drich@.UUCP (Dan Rich)

Just a dumb niggle (so why the long note?):

In article <1013@dialogic.UUCP>, drich@.UUCP (Dan Rich) writes:
>We have chosen the characters C-~ (or C-^ on some terminals)
                               C-^     C-~

The VT100 has it wrong, folks, and this ain't the first time.  The way
to print a control character is to print a C- (or a ^) and then print
the printing character whose ascii value is 64 greater.  These are the
32 characters generated by:

 (progn (setq i 0)
        (while (< i 32)
          (insert (char-to-string (+ i 64)))
          (setq i (1+ i))))

that is (try it!):

  @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_

~ has the value 126.  C-~ would be the character whose code is 126-64,
or 62.  This character is > .

Some people express rubout as ^?.  This obeys the above prescription
if you make the operator a bitwise XOR instead of plus; ? has the code
63 and RUB 127.

Another rule would be "take the remainder mod 32 of the character
code".  C-~ works by this rule, but there is no guidance to make this
the representation preferred to C-> or C-^, since it is a many-one
rule.  Also, the rule needs an exception for C-? (as RUB), which needs
to be distinguished from C-_.

Apologies to those of you who can't see tilde or caret or underscore
or square- or angle-bracket characters; this note must be very
confusing.
--
/jr, nee John Robinson     Life did not take over the globe by combat,
jr@bbn.com or bbn!jr          but by networking -- Lynn Margulis