[TUHS] B Source Code

Alec Muffett alec.muffett at gmail.com
Thu Sep 14 15:33:05 AEST 2017

I only know what this means due to a stint on GCOS-3 and having my
boss/sysmgr explain that "threaded code" in the old sense could be smaller
than the equivalent CISC binary on the same machine:


And no, it's not Threads :-)

- alec

On 14 Sep 2017 6:50 am, "Larry McVoy" <lm at mcvoy.com> wrote:

> Doug, could you talk about this some more?  Sort of like Reddit's
> explain it like I'm 5?  Assume I'm dense but want to learn and tell
> me how this worked again.  Threaded?  I'm guessing you mean that it
> did paging, did that need threads in the current sense?
> On Wed, Sep 13, 2017 at 11:48:44PM -0400, Doug McIlroy wrote:
> > > Check out:  ybc: a compiler for B <https://github.com/Leushenko/ybc>
> >
> > >From a historical standpoint, a plain B compiler lacks a very important
> > attribute of B in Unix. Yes, B presaged some C syntax. But its shining
> > property was that it produced threaded code, for which both compact
> > and expanded runtime support was available. The latter had software
> > paging. Thus B transcended the limited physical memory of the early
> > PDP-11s.
> >
> > If you can't compile something, you can't run it.  A prime example was B
> > itself. Without software paging it would not have been able to recompile
> > itself, and Unix would not have been self-supporting.
> >
> > Doug
> --
> ---
> Larry McVoy                  lm at mcvoy.com
> http://www.mcvoy.com/lm
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