[TUHS] Re: What is the intermediate code generated by the bc interpreter?

[Tom Teixeira <tjteixeira@earthlink.net>]

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On 5/11/25 6:28 AM, Jackson Helie G wrote:
> I checked Dennis M. Ritchie's "Users' Reference to B" and found an 
> example of implementing a B program at the bottom of the manual. It 
> said that bc generates intermediate code suitable for ba, and then ba 
> generates assembly code. So, I am curious about what the intermediate 
> code generated by bc is?

I found this reference 
(https://www.softwarepreservation.org/projects/BCPL/cambridge/Richards-Bootstrapping_BCPL-1973.pdf) 
written by Martin Richards about the intermediate code of BCPL. I never 
saw or used B, but this is one possibility.

But it seems very different from C compilers prior to the Portable C 
Compiler, even though code generation was table driven 
(https://wolfram.schneider.org/bsd/7thEdManVol2/ctour/ctour.html).

Note, before the RTS group at Project MAC started using UNIX, we had a 
home-written operating system for PDP-11/45 and PDP-11/70. I got a BCPL 
compiler from somewhere and made some enhancements - such as direct 
support for external variables and routines using a linker rather than 
the pure BCPL global array. When RTS got access to a VAX-11/780 running 
VMS, I was able to modify the Sixth or Seventh edition C compiler to 
generate code for the VAX-11/780 and wrote enough of a compatibility 
library to port various C programs to VMS. All that vanished once we 
were able to install 4BSD on the VAX-11/780. The machine was shared by 
the people doing the NIL project (New Implementation of LISP) on the 
VAX. I don't remember the details, but this paper coauthored by Guy 
Steele (https://www.dreamsongs.com/Files/HOPL2-Uncut.pdf) implies that 
NIL shifted their efforts to a different target machine: "In 1978, 
Gabriel and Guy Steele set out to implement NIL [Brooks, 1982a] on the 
S-1 Mark IIA, a supercomputer being designed and built by the Lawrence 
Livermore National Laboratory [Correll, 1979; Hailpern, 1979]."

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