[Simh] pdp11 and unix

[Johnny Billquist]

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 <will.senn at gmail.com
>> <mailto:will.senn at gmail.com>> wrote:
>>
>>
>>
>>     Sent from my iPhone
>>
>>     > On Feb 26, 2016, at 5:28 PM, Nigel Williams
>>     <<mailto:nw at retrocomputingtasmania.com>nw at retrocomputingtasmania.com>
>>     wrote:
>>     >
>>     >> On Sat, Feb 27, 2016 at 10:24 AM, Johnny Billquist
>>     <bqt at softjar.se <mailto:bqt at softjar.se>> wrote:
>>     >> On 2016-02-26 23:47, Eric Smith wrote:
>>     >>>> On Feb 25, 2016, at 9:26 PM, Gregg Levine
>>     <gregg.drwho8 at gmail.com <mailto:gregg.drwho8 at gmail.com>
>>     >>>> <mailto:gregg.drwho8 at gmail.com
>>     <mailto:gregg.drwho8 at gmail.com>>> 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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>
>
>
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-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol