(Excerpts from a message dated 08-28-99, Roy J. Tellason to David
Bowerman)

Hi Roy--

 JdBP> I think it's about time that we let go of this CP/M nonsense.

 RJT> Agreed.  It was only put _in_ to CP/M in the first place because
 RJT> the CP/M directory structure does not store the exact size of a
 RJT> file.  It certainly doesn't have any place in a 32-bit OS...

 DB> The convention of using a ctrl-Z to denote EOF predates CP/M
 DB> by a fair chunk. 

RT>I wouldn't doubt it...

RT>Let's see,  I'll bet they used that in that RT-11 OS I 
  >played with back in '78 or so,  do you think?  :-)

    There is no way that anyone can blame the use of Ctrl-Z as an EOF
mark on any desktop operating system :-).

    Ctrl-Z (1fh) has been part of the ASCII 7-bit code since its
beginning (around 1960, IIRC).  The first three of the four "separator"
control characters, 1ch through 1eh (, , and ) were
originally intended for data transmission segment separators.  IIRC,
Ctrl-Z  was the "user-defined separator" to be used in other
environments.  IMO, ASCII was originally devised to accommodate AT&T,
who realized that the 5-bit Baudot code (used previously for TTY
systems) was no longer sufficient for "modern" data transmission.  The
computer manufacturers were snookered into going along with the 7-bit
idea, because (at the time) nobody (except IBM) was contemplating any
computer character codes having more than six bits (and IBM wasn't
making public noises about System/360 at the time).  Later, Ctrl-Z was a
convention adopted by the computer manufacturers as an EOF mark for the
new 8-bit tape-drive systems.

    ASCII became a computer problem in 1964 with IBM's announcement of
the 8-bit System/360 and its associated 8-bit (plus parity) tape drives.
The ANSI committee met to decide how to "embed" seven-bit ASCII in the
new 8-bit medium.  Officially, ASCII is still a 7-bit code: the eighth
(high-order) bit in "true" ASCII embodiments is always zero!  The eighth
bit was put to use (for desktop machines) in the IBM PC (1981) with the
IBM-defined "extended ASCII" that made the top 128 characters available
for keyboard input, but has never been adopted as an official standard.

    Regards,

        --Murray

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