[Simh] pdp11 and unix

[Will Senn]

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
>     <nw at retrocomputingtasmania.com
>     <mailto: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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>     > Simh at trailing-edge.com <mailto:Simh at trailing-edge.com>
>     > http://mailman.trailing-edge.com/mailman/listinfo/simh
>
>     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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