[mikeash]

Thanks for the details. I find these environments fascinating, although I'm sure they're best observed from a great distance in both space and time.

One more question, if I may: once you got used to it, what was the productivity like? I imagine these sorts of things as taking days or weeks to make the simplest of changes, but maybe the horror I imagine becomes routine after a year or two of experience.

[jloughry]

It took less than two weeks to become fluent (I started writing the annotator tool around that time). Probably, it was the well-developed---if informal---methodology that Annie, the experienced programmer who took me under her wing when I arrived, taught me. She made a little ceremony of it, giving me my copy of the binder that held all of the accumulated knowledge about the reverse-engineered language in its photocopied pages, showing me how she used different coloured highlighter pens to tie together things in a listing, and giving me little example programs to understand. I studied diligently; it was like working crossword puzzles. About two weeks later, I was promoting my first changes to the test environment.

Edited to add: I never got over the white-knuckle feeling of it: everything global, limited supply of working-storage variables that were constantly being re-used, and interactions that could bite from a distance. One of the most useful features of the LIST annotator was that it generated an ordered cross-reference listing that could be directly compared. That feature made choosing safe working-storage variables a much safer activity.