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

Hi, thanks for mentioning my project! I recently ported the compiler to ITS on the PDP-10 and had to revisit the question of the intermediate code. My take is that it was probably an ASCII code and not all too different from PDP-7 assembly. One striking difference between the PDP-7 and PDP-11 interpreter that have survived is the handling of lvalues. Taking the address of something is done by an operator (u1) in the PDP-7 interpreter, whereas on the PDP-11 this is handled somewhere in the compilation process, and in addition to the automatic (a) and external (x) operators there are now lvalue versions of them (va and vx). I very very strongly suspect that this is handled by the B assembler and not the compiler. Two other questions are where the 'i'-versions of the a/x/c operators and the control flow of the conditional ?: operator were handled. For the latter i concluded it had to be the assembler, although the label numbers in printf.o are in line with those that would have been generated by the compiler. In contrast, the first and second pass of the C compiler use different ranges of labels. Unfortunately all these questions appeared and became clearer only over time and as a result there are various incarnations of my reconstructed compiler in the github repo....I should really make a push to clean it up a bit better, it's a complete mess. You may also want to check out my talk on B at VCFB 2024: https://www.youtube.com/watch?v=OLDTPlLa1bI Cheers, aap On 12/05/25, Thalia Archibald via TUHS wrote: