BASIC-Plus decompiler

John> At 12:25 PM 8/6/2008, Paul Koning wrote: John> As has happened many times before, the same topics get rehashed John> on this list even by the same people. ... John> http://elvira.stacken.kth.se/rsts/rsts_80th_birthday.html John> 1974 February-Clark Baker, George Robbins, Dan Grim and Ed John> Baker write the PPCODE Basic Plus Decompiler. John> 1978: October-Nick de Smith returns to Dulwich College, where John> he had been a student between 1967 and 1976, to write the John> DECOMP Basic Plus Decompiler. John> 1990: July-SPL announces special anniversary ?offers? on John> various software products including The Link, BAS24K, BP3, RPM, John> DECOMP, SORT1 and REPGEN. John> (The name George Robbins caught my eye, as I knew him from John> Commodore and the Amiga. Other googling makes it apparent it's John> the same guy who worked on the 1974 decompiler, and sadly, it John> seems he passed away in 2002.) John> Perhaps we're just arguing about semantics. If BP2 was a true John> compiler, to me that means it was emitting native CPU code in John> an executable format - no interpretation needed. So you're John> saying this decompiler was reading CPU opcodes and mapping them John> correctly back to BASIC code? That it wasn't just detokenizing John> something that ran through an interpreter? John> ... http://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/decus/1… John> "[80,19] BASIC-PLUS-1 DECOMPILER: two programs, one data file John> BASIC-PLUS-1 reverse compiler" You may be missing the different product names. "BASIC-PLUS" and "BASIC-PLUS-2" are very different beasts. (I haven't seen BASIC-PLUS-1 before, that wasn't a normal designation but the meaning is obvious.) BP was a P-code ("push-pop code") incremental compiler. It runs only on RSTS. BP2 was a regular compiler; it would produce object files which you'd feed to TKB to get your RSX-format executables. It ran on RSTS, RSX, and VMS. BP though not exactly. You could certainly write the intersection of the two very easily. At DEC, that was the practice for RSTS tools because, at least for a while, they needed to be useable for customers who didn't have the BP2 optional (extra cost) product installed. Later that was dropped due to the introduction of "CSPCOM", a limited BP2 variant. The decompilers you're describing are for BP, not BP2. PPcode was just "high level" enough that you could get reasonably intellegible decompile output. I don't think the decompile would actually produce BASIC source; instead it was more like an annotated disassembly that you could read with some effort. At least that's what I recall from the one or two occasions where I tried one of those decompilers. There are several other DEC BASICs as well. There was one for DOS; I don't remember anymore what that one looked like. It may have been a straight interpreter (stores text, interprets text). Some vague memory says that it used an oddball 3 word (48 bit) float format, quite unlike any of the ones supported by PDP-11 hardware FPUs. Or that may have been the BP in RSTS V3. Or both... Then there was BASIC-11 for RT-11. That was a much more limited BASIC, nowhere near as powerful as BP or BP2. It was a tokenizing system: the interpreter would execute from the tokens but that wasn't a P-code, it really was only a different way of representing the source text. When you said "LIST" it would reconstitute the source code from the token stream, so the layout would be altered a bit. It used PDP-11 standard floating point format. By contrast, BP did support "LIST" but it would do that by saving the source text (in a temporary file) as well as the P-code representation; LIST would give you the saved source text. paul