A general housekeeping plea. When quoting someone's text, could we please use correct attributions? On Sat, Jul 13, 2024 at 7:46 PM John Levine <johnl(a)taugh.com> wrote: It may appear so based on the quoted text, but in fact Doug did _not_ write the words reproduced here, but rather, was quoting someone else who did. In this case, Aron Insinga wrote the text below. Unfortunately, that this is Aron's contribution to the discussion is not mentioned anywhere in the quoted portion. Of course mistakes happen, but it's been happening with increasing frequency lately, and it's not particularly fair to either the person who made the original contribution or the person to whom the quotes are misattributed. Thanks! - Dan C.

On 7/13/24 19:46, John Levine wrote: Possibly, but they use 'syllables' for tokens (symbols or integers), and they say here that they advance the location counter after each word copied.  If they were copying characters into the input stream, they would not be incrementing the location counter ('.') after each word transferred. And as you say, it is simple parameter substitution, so tracking which macro argument goes into which instruction's address field is easy.  The instruction format is simple.  So for each line in the macro definition body, if the opcode is a memory reference instruction, put the argument number in the binary instruction address field before storing the instruction word in a list/block. When expanding the macro, if the opcode is a memory reference instruction, get the argument number from the address field and replace it with the symbol table value of the symbol passed in as the actual argument, and store the word in the output stream (and incrememnt '.'). I haven't yet gotten the 18-bit-but-incompatible PDP-4 documentation for comparison.  [IIRC the PDP-4 assembler was the one with a single pass assembler that punched the symbol table at the end of the tape, and the clever loader that read the tape upside down and backwards to first rebuild the symbol table and then fix up the instructions and load them into memory.] - Aron

On 7/14/24 14:02, John Levine wrote: Thank you!!  I found the PDP-1 and TX-0 MACRO sources and was sadly unsurprised by the lack of comments, so they are difficult reading. http://www.bitsavers.org/bits/DEC/pdp1/papertapeImages/20040106/macro_6-63/… They are not storing tokens.  In fact, the list of 'codes' for items stored as the macro body on p 20 is:     a storage word,     a dummy symbol specification.     a constant,     a dummy symbol parameter assignment, or     an end marker. So it is not storing tokens for instructions, just storage words (instructions or data) as mentioned in the user manual. In the discussion in the internals manual, after the paragraph mentioning the year this was designed (a nice touch), they say that they are storing the macro body as 'partially assembled' 'words' into which the dummy symbols are 'inserted'.  (And in a single-address architecture with a small memory address, addition is enough to do that insertion.)  They explain why they did this instead of storing characters: They do not look at the opcode as I suggested was possible, they have a more general solution that works for a word containing either code or data. I think that this may be (at least as far as any of us know) a unique case from the early days of computing where, on the TX-0 and a port to the PDP-1, a macro body *is* stored as a list of 'machine words' instead of source text.  The macro  body is not manipulated as a 'higher-level construct', it is just used for quite limited macro expansion. This has NO bearing on what DEC/HP/VSI did more than two decades later for the Alpha, Itanic, and x86_64 (where macros are expanded by the conventional insertion of characters from the macro body into the source text stream). - Aron