> From: John Cowan
> Rather than starting another process, the Multics shell mapped the
> executable program the user requested into its own space .. then jumped
> into it. The equivalent of exit() simply jumped back to the shell code.
This is from memory, so apply the proverbial grain, but ISTR that the
original concept for the Multics shell was just like that for Unix - i.e.
each command would be a separte child process. This was given up when Multics
processes turned out to be so computationally expensive, and they went to
commands being subroutines that were dynamically linked in (very easy with
Multics, where dynamic linking was a fundamental system capability) and
called from the shell.
So what is the etymology of "shell", then? I see that Multics has a shell. Was the CTSS user interface also called a shell?
Sent from my Android phone with K-9 Mail. Please excuse my brevity.
Wikipedia is by nature a *summary of the published literature*. If you
want to get some folklore, like what "cron" stands for, into Wikipedia,
then publish a folklore article in a journal, book, or similar reputable
publication. Random uncontrolled mailing lists simply do not count.
That sounds fair enough on the surface.
But if you follow the references cited to support the cron
acronyms, you find that random unsupported assertions in
conference papers do count. That's not a lot better.
I'd like to see a published, citable reference for the
true origin of `cron'. Even better, better published
material for a lot of the charming minutiae of the early
days of UNIX. (Anyone feel up to interviewing Doug and
Ken and Brian and whoever else is left, and writing it up
for publication in ;login:?)
But I'd be satisfied if we could somehow stamp out the
use of spurious references to support spurious claims.
If I had the time and energy I'd look into how to challenge
the cron acronyms on those grounds. Any volunteers?
> From: Will Senn
> 000777 HALT
That's actually "BR ."; the difference is important, since the CPU (IIRC)
doesn't honour DMA requests when it is halted, and DMA needs to be working for
the controller to read that first block (a secondary tape bootstrap) into
> This seems like gobbledegook to me.
> It moves the MTCMA (Magtape Current Memory Address) into R0, then it
> moves the MTCMA into the MTBRC (Magtape Byte Record Count)
"The address of the MTCMA into", etc. Looking quickly at the programming spec
for the TM11 controllers, it wants a negative of the byte count to transfer in
this register; the address of the MTCMA just happens to also be a large enough
negative number to be usable as the (negative) size of the transfer request.
(The first record is probably shorter than that, but that doesn't matter.)
Note that this code could probably also have been written:
MOV #172524, R0
and been equally functional.
> then it moves 60003 into the MTC (Magtape control register), which
> causes a read operation with 800BPI 9 Channel density.
I'm too lazy to look at the programming spec for the details, but that sounds
> Am I misinterpreting the byte codes or is this some idiosyncratic way to
> get the Magnetic tape to rewind or something (the TM11 has a control
> function to rewind, so it seems unlikely that this is the case
No, it's just the shortest possible program to read the first block off the
It depends on i) the operator having manually set the tape to the right point
(the start of the tape), so that it's the first block that gets read, and ii)
the fact that the reset performed by hitting the 'Start' key on the CPU clears
the TM11 registers, including the Current Memory Address register, so the
block that's read is read into memory location zero.
Hence the direction to 'once the tape has stopped moving, re-start the CPU at