On Fri, Jul 1, 2022 at 10:03 AM Steve Nickolas <usotsuki@buric.co> wrote:

> On Fri, 1 Jul 2022, Nelson H. F. Beebe wrote:
>
> > Ctrl-D signifies end of transmission.  Some other O/Ses have used
> > Ctrl-Z for that purpose, presumably because Z is the final letter
> > of numerous alphabets.
>
> I thought only CP/M and its descendants did that. :o (Of course that
> includes DOS and Windows)
>
Steve - The social disease spread of DOS-11, RT-11, CP/M, and MS/PS-DOS
used ^Z as an EOF character in their text file format.  The key is that
they stored a block count, not a byte count in the META.   Thus the last
byte needs a marker to tell the OS to stop reading. [Early DEC OS's may
have done that also, but I never looked at their FS formats].

Unix, of course, never made any distinction to the core OS WRT to 'type'
[other than Regular/Directory/Special]  and Ken stored a character count.
So there was no need to signal EOF with a markered stored on disk..

A pipe or the shell on the other hand does have a need to signal the end of
a transaction, and 'End of Transmission,' as Nelson points out, is the
ASCII character reserved for the same.

ᐧ