1 Jul
2022
1 Jul
'22
1:31 p.m.
> I don't know the answer to Ctrl-D.
The Unix command "man ascii" has the answer:
Oct Dec Hex Char Oct Dec Hex Char
------------------------------------------------------------------------
000 0 00 NUL '\0' 100 64 40 @
001 1 01 SOH (start of heading) 101 65 41 A
002 2 02 STX (start of text) 102 66 42 B
003 3 03 ETX (end of text) 103 67 43 C
004 4 04 EOT (end of transmission) 104 68 44 D
....
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.
There is a good book about the history of character sets (pre-Unicode)
in the book described at this URL:
http://www.math.utah.edu/pub/tex/bib/master.html#Mackenzie:1980:CCS
Bob Bemer (1920--2004), known as Dr. ASCII to some of us, was a key
person in the standardization of character sets:
https://en.wikipedia.org/wiki/Bob_Bemer
https://en.wikipedia.org/wiki/ASCII
-------------------------------------------------------------------------------
- Nelson H. F. Beebe Tel: +1 801 581 5254 -
- University of Utah -
- Department of Mathematics, 110 LCB Internet e-mail: beebe(a)math.utah.edu -
- 155 S 1400 E RM 233 beebe(a)acm.org beebe(a)computer.org -
- Salt Lake City, UT 84112-0090, USA URL: http://www.math.utah.edu/~beebe/ -
-------------------------------------------------------------------------------
1 Jul
1 Jul
2:02 p.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
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)
-uso.
3:01 p.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
On Fri, Jul 1, 2022 at 10:03 AM Steve Nickolas <usotsuki(a)buric.co> wrote:
On Fri, 1 Jul 2022, Nelson H. F. Beebe wrote:
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
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)
7:22 p.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
Early use of ASCII control characters was ALL over the map.
I remember typing in a BASIC program to approximate PI during a
college tour in the late 70's, and whatever system they had (maybe
Univac?? there was an unplugged RCA Spectra in the hallway) required
typing Control C (ASCII ETX) instead of RETurn on the teletype.
*THAT* was a mind-f*ck!
Clem Cole wrote:
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].
I TEND to think of the DEC ASCII traditions as coming out of the PDP-6
Monitor (later TOPS-10), which probably dates to c. 1964, and modern
Unix/Linux systems are almost fully infected with DEC conventions
(DELETE, CTRL/U, CTRL/C vs @/#/DELETE for example), except for ^M and ^Z.
The earliest version I have on hand is version 3.19, which includes
PDP-10 (KA10) support (c.1968). The scheduler (CLKCSS) has Tom
Hastings name on it, dated 6 SEP 67. Tom wrote the MIT CTSS
(timesharing on IBM 709/7090) scheduler, and the DEC T/S system
mirrors CTSS in many ways (project/programmer numbers). CTSS used
ASCII, and it would be interesting to know what conventions were used
there!! On topic: Ken might know. @/# seem to have been used on
Multics.
The full duplex terminal code (SCNSRF) with Robert Clemmens name
on it, dated "27 NOV 68" has the following conventions:
Use of "^Q" as a convention for control characters.
CR ^M return to column zero (used alone in files for overstrike)
LF ^J line feed: line terminator
HT ^I horizontal tab
VT ^K vertical tab (n line feeds on a TTY)
FF ^L form feed
XON ^Q start TTY paper tape reader
XOFF ^S sent by TTY PTR on end of tape?
^U clear input line
^Z EOF
0177 DEL delete a character
033,0175,0176 "ALTMODE" -- used in DDT (& TECO), echoes as "$"
I don't have a set of Commonly Used System Programs (CUSPs) from that
era, so I can't see how they handle ^Z if they see it in a file.
I don't remember seeing ^Z in disk files on TOPS-10.
A quick look at the 3.19 code (I rescued it from six DECtapes while at
DEC; three each for full & half duplex versions of the code!) and
didn't spot the on disk/DECtape metadata formats, but I suspect they
were just block counts. There ARE files I've pulled off of tape with
embedded NULs, so I suspect code was written to ignore NULs whereever
they appeared. "Dump Mode" I/O, where you passed IOWDs -COUNT and
WORD_POINTER in halfwords, rather than transferring character at a
time into a buffer, was a way to speed up disk I/O, which would easily
result in multiple embedded NULs. My recall is that we thought of
disk files as made up of blocks, and not characters.
MIT AI's Incompatible Timesharing System (ITS), a dig at CTSS (and DEC
as well?) used ^C instead of ^Z for EOF, appearing (in triplicate?)
inside of (older) files. And ^Z stop a (sub)job and drop into DDT (the
debugger *AND* command interpreter), which could be examined,
continued, or killed (ALT CTRL/X). I've always assumed BSD used ^Z as
the suspend character for this reason.
TOPS-20 (and perhaps later day TOPS-10) had file metadata
indicating file byte counts, and byte sizes (1-36 bits), but
TOPS-20 ALSO only allocated file storage on a page basis (512
36-bit words instead of the TOPS-10 256W block size).
The PDP-7 unix inode stores a word count, rather than a byte count,
and ISTR programs ignore NULs for the same reason.
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.
I don't know the rationale for DEC's use of ^Z for EOF, but as I
pointed out above, use of ASCII control characters wasn't widely
standardized in the 70's (is it today?)
To pull the thread back to the list topic
1. Remember which of @ and # deletes a single character.
2. Fix a filesystem without fsck.
3a. Buy a controller card to be able to use a disk
3b. Write a driver for a third party controller.
4. Edit a driver and recompile the kernel to change partition sizes.
5. Use dd to convert a mainframe tape to variable line length ASCII.
6. Wonder whether something with a serial port is a DTE or a DCE.
7. Figure out the serial port settings for a terminal/modem:
data bits, parity, stop bits.
8. Adjust jumpers on a peripheral
9. Insert or remove wires for IRQ bus continuity
Non-UNIX related:
Punch job control cards.....
Burst fanfold paper by flicking their finger, to get your printout.
Spread out fanfold paper on the floor to get a "big view"
.......
7:53 p.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
Phil nice list.
On Fri, Jul 1, 2022 at 3:23 PM Phil Budne <phil(a)ultimate.com> wrote:
Doing the same with adb(1) on the kernel binary
as well as understanding disk geometry and calculating the HEAD/CYL/SEC to
block numbers properly.
> 6. Wonder whether something with a serial port is a DTE or a DCE.
How about knowing what DTE and DCE mean in the
first place.
Along with why CTS/RTS (HW) flow control was really needed at high speed.
Why the UNIX community tended to migrate to aftermarket DH11, instead of
DZ-11s - particularly for UUCP
> 8. Adjust jumpers on a peripheral
How about having the proper jumper sizes. Or
realizing the DIP switches
were not actually toggling properly so the address was wrong.
> 9. Insert or remove wires for IRQ bus continuity
Know what a BUS GRANT card does.
ᐧ
I've always assumed BSD used ^Z as the suspend
character for this reason.
Yes, Kulp's Job control for the PDP-11 was based on his ITS experience.
Joy picked it up from Kulp.
The other big gift to UNIX from ITS was Eric Shienbrood's more(1) command
[discussed elsewhere].
This brings us back to the topic -- the need for more(1) as either built-in
like ITS or as command [UNIX] is lost with today's infinite scroll buffers.
To pull the thread back to the list topic
2. Fix a filesystem without fsck.
Much less, what was fsck(1) original name at CMU ;-) or why tjk wrote the
first version.
4. Edit a driver and recompile the kernel to change partition sizes.
2 Jul
2 Jul
7:36 p.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
Clem Cole <clemc(a)ccc.com> writes:
On Fri, Jul 1, 2022 at 10:03 AM Steve Nickolas
<usotsuki(a)buric.co> wrote:
But that's a common misconception and not how Ctrl-D works on Unix.
Ctrl-D is part of the terminal discipline and causes an immediate stop
of the current read(2) syscall. If nothing is in the input buffer,
this causes a zero-length read which is detected as end of file.
You can verify this e.g. by typing "foo<Ctrl-D>" into cat(1). It will
print "foo", but not exit. Another Ctrl-D will then quit cat(1) due
to the empty read.
In no case, a ASCII Ctrl-D 0x4 is sent over a pipe or to a shell.
(Over the pty, yes.)
cheers,
--
Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/
On Fri, 1 Jul 2022, Nelson H. F. Beebe wrote:
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. 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)
7:50 p.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
On Sat, Jul 2, 2022 at 3:36 PM Leah Neukirchen <leah(a)vuxu.org> wrote:
But that's a common misconception and not how
Ctrl-D works on Unix.
Point taken and my bad on my explanation. Absolutely, any characters can
be stored or read/written in a file. As you explained, the *interpretation*
of the character is done elsewhere and my words could have been
misunderstood by my lack of precision.
In fact, tools like uucico and IP over serial all required a full 8-bit
path without any interpretation through the terminal handler and would have
needed other tricks like escaping to have been made to work otherwise.
But what I did say was true. The question was why ^D and I pointed out
that the ASCII EOT character was picked for the characters for the
terminal handler to use when it needs to make the distinction of when this
is the end of the input sequence - i.e. EOT. Moreover, we were discussing
a number of chars being processed by the terminal handler such a # @ <DEL>
vs. ^H ^U ^C or SW flow control ^S/^Q, Job Control ^Z/^T and the like.
mei cupla for not being more clear.
ᐧ
3 Jul
3 Jul
12:22 a.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
But that's a common misconception and not how Ctrl-D works on Unix.
Ctrl-D is part of the terminal discipline and causes an immediate stop
of the current read(2) syscall. If nothing is in the input buffer,
this causes a zero-length read which is detected as end of file.
I once read a Patricia Cornwell novel in which the plot hinged around some
crooked person typing
cat > ttya
Somebody is coming
meaning to send a message to /dev/ttya, but instead, creating a file named
"ttya".
(I almost surely have the details wrong, but I'm too lazy to go searching
for the real quote, which isn't relevant here.)
Cornwell said the ttya file was of size 18, so, being an obsessive
nit-picker, I sent her a letter saying that it could have been 18 bytes
long,
but that would imply that the sender terminated the message with CTRL-D
rather than a newline and then terminating the command,
the latter of which seemed much more plausible for a novice user. Rather
than ignoring my letter, or telling me where to shove my letter,
she sent me a gracious thank you note, and an FBI hat, which I still own.
On Sat, Jul 2, 2022 at 3:37 PM Leah Neukirchen <leah(a)vuxu.org> wrote:
Clem Cole <clemc(a)ccc.com> writes:
of
On Fri, Jul 1, 2022 at 10:03 AM Steve Nickolas
<usotsuki(a)buric.co>
wrote:
On Fri, 1 Jul 2022, Nelson H. F. Beebe wrote:
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 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)
a transaction, and 'End of
Transmission,' as Nelson points out, is the
ASCII character reserved for the same.
But that's a common misconception and not how Ctrl-D works on Unix.
Ctrl-D is part of the terminal discipline and causes an immediate stop
of the current read(2) syscall. If nothing is in the input buffer,
this causes a zero-length read which is detected as end of file.
You can verify this e.g. by typing "foo<Ctrl-D>" into cat(1). It will
print "foo", but not exit. Another Ctrl-D will then quit cat(1) due
to the empty read.
In no case, a ASCII Ctrl-D 0x4 is sent over a pipe or to a shell.
(Over the pty, yes.)
cheers,
--
Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/
1 Jul
1 Jul
3:50 p.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
Steve Nickolas wrote:
Nelson H. F. Beebe wrote:
Also TOPS-10. And proably other DEC operating systems, but I don't know
much about those. I believe CP/M was inspired by many of the DEC
traditions,
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. 
4:20 p.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
On Fri, Jul 1, 2022 at 9:50 AM Lars Brinkhoff <lars(a)nocrew.org> wrote:
Steve Nickolas wrote:
VMS, TOPS-20, RT-11 and RSTS/e did as well. Presumably RSX did too since
DEC tried hard to keep RSX/VMS 'finger compatible' though I have no first
hand
experience with RSX to say for sure.
Warner
Nelson H. F. Beebe wrote:
Also TOPS-10. And proably other DEC operating systems, but I don't know
much about those. I believe CP/M was inspired by many of the DEC
traditions,
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.
6:18 p.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
On Fri, Jul 1, 2022 at 12:22 PM Warner Losh <imp(a)bsdimp.com> wrote:
since DEC tried hard to keep RSX/VMS 'finger
compatible' though I have no
first hand
experience with RSX to say for sure.
Hrrmpt... maybe/sort of/after a fashion ... as a UNIX guy and someone
that lived it (much less an ex-DECie), I famously argued with Cutler that
he didn't! [It's a good beer story for some time in person, but not
really for TUHS other than to say it happened, and it was a VMS *vs*. UNIX
debate between DC and myself one night at the old Maui Kai in Littleton, MA
with our old common boss rsg (*a.k.a.* Fossil) acting as the referee]
ᐧ
6:09 p.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
On Fri, Jul 1, 2022 at 11:50 AM Lars Brinkhoff <lars(a)nocrew.org> wrote:
I believe CP/M was inspired by many of the DEC
traditions,
If you do some Internet searching, there is an interview (IIRC from Byte
Magazine in the late 1970s) where its author (Gary Kildall) straight out
said he was trying to emulate RT-11 for an 8080. The funny thing to
remember is that Kildall was a language guy, he wrote CP/M to demo his
programming language PL/M for Intel. The demo ended up having more
longevity than the tool he was trying to sell.
ᐧ
6:45 p.m.
New subject: "9 skills our grandkids won't have" - Is this a TUHS topic?
On Fri, 1 Jul 2022, Lars Brinkhoff wrote:
Steve Nickolas wrote:
Yeah. As, independent of its position as a knockoff CP/M, was the
original MS-DOS (2.0 brought in a few things from Xenix).
-uso.
Nelson H. F. Beebe wrote:
Also TOPS-10. And proably other DEC operating systems, but I don't know
much about those. I believe CP/M was inspired by many of the DEC
traditions, 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.
656
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12 comments
8 participants
participants (8)
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Clem Cole -
John P. Linderman -
Lars Brinkhoff -
Leah Neukirchen -
Nelson H. F. Beebe -
Phil Budne -
Steve Nickolas -
Warner Losh