As far as I know/understand, AT&T didn't have any DEC OS or software for
the PDP-7. So it was, I guess, pretty natural to take what you did have,
and adopt it for your needs. They had the GE system, with an assembler
that could be used, with tweaks, so that's what they used. Getting some
OS from DEC for the PDP-7, in order to assemble their own OS, probably
seemed excessive. Also, remember that they didn't really have much of a
budget to buy stuff at that point.
Exactly where the PDP-7 originally came from, and what it had been used
for before would be interesting to find out.
Johnny
On 2016-02-27 02:28, Will Senn wrote:
Found this in Ritchie's article, "The Development of the C Language":
Thompson was faced with a hardware environment cramped and spartan
even for the time: the DEC PDP-7 on which he started in 1968 was a
machine with 8K 18-bit words of memory and no software useful to
him. While wanting to use a higher-level language, he wrote the
original Unix system in PDP-7 assembler. At the start, he did not
even program on the PDP-7 itself, but instead used a set of macros
for the GEMAP assembler on a GE-635 machine. A postprocessor
generated a paper tape readable by the PDP-7.
These tapes were carried from the GE machine to the PDP-7 for
testing until a primitive Unix kernel, an editor, an assembler, a
simple shell (command interpreter), and a few utilities (like the
Unix rm, cat, cp commands) were completed. After this point, the
operating system was self-supporting: programs could be written and
tested without resort to paper tape, and development continued on
the PDP-7 itself.
Thompson's PDP-7 assembler outdid even DEC's in simplicity; it
evaluated expressions and emitted the corresponding bits. There were
no libraries, no loader or link editor: the entire source of a
program was presented to the assembler, and the output file—with a
fixed name—that emerged was directly executable. (This name, a.out,
explains a bit of Unix etymology; it is the output of the assembler.
Even after the system gained a linker and a means of specifying
another name explicitly, it was retained as the default executable
result of a compilation.)
So, they didn't use DEC's assembler, but they used GE's?
Interesting stuff.
Will
On 2/26/16 6:26 PM, Clem Cole wrote:
If you were used to building your own tools, you might not. Also if
you are bootstrapping from something else (like a large timesharing
system from another manufacturer). You might put your tools on the
other system, until the new system could "self host."
We do the same things today.
Clem
On Fri, Feb 26, 2016 at 7:23 PM, Will Senn <[email protected]
<mailto:[email protected]>> wrote:
Sent from my iPhone
> On Feb 26, 2016, at 5:28 PM, Nigel Williams
<<mailto:[email protected]>[email protected]>
wrote:
>
>> On Sat, Feb 27, 2016 at 10:24 AM, Johnny Billquist
<[email protected] <mailto:[email protected]>> wrote:
>> On 2016-02-26 23:47, Eric Smith wrote:
>>>> On Feb 25, 2016, at 9:26 PM, Gregg Levine
<[email protected] <mailto:[email protected]>
>>>> <mailto:[email protected]
<mailto:[email protected]>>> wrote:
>>>>
>>>> Version Zero was hand coded on a PDP-7
>>>
>>>
>>> I know Gregg is right. But .. Can you /imagine?/
>> Not sure I understand this comment either. Are you suggesting
that coding an
>> OS is assembler is something exceptional or complicated, or
unusual?
>
> I took "hand-coded" to mean Version Zero was (initially) done
without
> an assembler, they wrote down the instructions in machine code.
>
> Perhaps not unusual for the 1960s but laborious none-the-less.
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I don't understand this. The PDP 7 had an assembler and debugger.
Wouldn't they have used the assembler to generate the bootstrap
system?
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|| on a psychedelic trip
email: [email protected] || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
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