[COFF] Re: ancient macros, machine code translation,as mental architecture models

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