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Reply-To: zeil AT cs DOT odu DOT edu
Subject: Re: how do i simulate a null character from the keyboard?
To: cygwin AT cygwin DOT com
Cc: emallove AT yahoo DOT com
X-Mailer: Lotus Notes Release 5.0.2b  December 16, 1999
Message-ID: <OFDDF8933A.F444C8BE-ON85256B67.0062B0FE@cs.odu.edu>
From: szeil AT notesmail DOT cs DOT odu DOT edu
Date: Thu, 21 Feb 2002 13:08:13 -0500
X-MIMETrack: Serialize by Router on lotus/ODUCS(Release 5.0.8 |June 18, 2001) at 02/21/2002
 01:08:14 PM
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Ethan Mallove <emallove at yahoo dot com> wrote:
>
>  why is ctrl-d a logout command
>instead of NULL?
>
Because that's what ctrl-d is supposed to be for!

In the ASCII character code set, ctrl-d is defined as the EOT
signal, short for "End Of Transmission".  So Unix (and
consequently Cygwin) were just following the published
standard.

NUL would, in general, be a terrible choice for an OS to
adopt because NUL characters have perfectly useful
applications in serial data streams (e.g., as something
that you can insert into a stream to affect the timing
without altering the message).

ctrl-z, by the way, used as the terminator by MSDOS and other
early PC operating systems was an unintentionally humorous
choice. It's defined as the SUB character, used as
a placeholder to indicate the data lost during a garbled transmission.

Steve Z



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