Catching Up

Catching up on some software updates.

Time to catch up on announcements…

• Some may have noticed already, but some time ago the Virtual 6502 suite received an update on its GUI, featuring both dark and light mode.
• Maybe somewhat less obvious, the assembler now supports anonymous (or temporary) labels. Meaning, you can mark any address/instruction by a “!” or a colon (“:”) for an empty label at the start of the line and may refer to this by an “!” or a colon and any number of plus or minus signs as a quantifier as a target address, where “!-” refers to anonymous label immediately before and “!++” to the second-next anonymous label and so on. (E.g., “BNE !+” may be a useful construct, where you just want to skip a couple of instructions and do not want to think of yet another label for this.)
• The disassembler received an option to include cycle counts as comments for each instruction. And there’s a new option to format the output to lower-case.
• And, I redrew some diagrams for the 6502 instruction sheet in hand-coded SVG :-), so blurry scans no more.
• Last fall, the Virtual 6502 suite also received support for the BBC Micro (or Acorn 8-bits in general) and the assembler integrated in BBC BASIC. I had planned a write-up on this, but this somehow vanished in the cracks. Anyways, in order to assure round-trips through the entire suite, this eventually involved parsing and executing some BASIC instructions, as well, especially string functions. (This is mostly for the peculiar indirection mechanism of BBC BASIC Level I, which doesn’t feature any constructs for including any literals directly in the assembler code, but requires a break-out to BASIC in order to insert values into memory by the help of some special BASIC variables. As this is used mostly for strings, this afforded some BASIC string processing capabilities, as well, in order to run/process actual BBC BASIC sources. This is also includes a basic “understanding” of FOR-loops, at least enough to recognize the loop variable and to ignore them otherwise. You get the idea… Retrofitting this to what was once a very simple assembler was a bit of an adventure. However, there’s now a “BBC Micro” checkbox to each of the applications for doing the 6502 BBC-style.)
• Finally, there’s a minor bug-fix to the emulator and the disassembler, where we attempted to output a character literal for 0x7F, which is a non-printable character.

Moreover, the Digital Library finally features Wittgenstein’s tractatus logico-philosophicus, which had been a safe bet for a candidate right from the beginning, because the unique proposition numbers of the tractatus and sequence numbers are a match made in heaven — or hell (you decide) — at least not at ground level. Diagrams are a bit difficult, though. (We have to admit, however interesting this may be, the inprint of punch card remains a somewhat questionable choice of media for literature.)