Nev Dull - 2000
2001 archives 2002 archives 2003 archives 2004 archives this yearA quick scan didn't turn up any mention of one of the more interesting aspects of the HP-67 programming, which got carried on to ludicrous excesses by avid 41c fans: "Synthetic Programming". They do have a nice writeup of 41c synthetic programming, but I couldn't find anything on the HP-67 version which preceeded it.
On the '67, someone figured out a bizarre sequence of keystrokes and carefully-timed interruption of the power (done by using a momentary-break switch hooked in with a carved sliver of copperclad PC board so it got into the power circuit through the charger jack) that allowed getting otherwise-inaccessible opcodes; people trial-and-error mapped out all possible opcodes for the CPU, and found some that allowed displaying glyphs not otherwise accessible in the 7-segment LED display, and (I think, my memory is pretty faint here) maybe some extra programming instructions. It required pretty much scrambling the state of the machine to get at these things, but once you got one, you could store it on the magnetic card, reset the machine to a normal healthy state, then get it back off the card to incorporate it into programs. Since the '67 was a ROM+RAM machine this wasn't too nasty; power cycle brought it back to a nice normal state.