PL/I was my favorite mainframe programming language my last two years as
an undergrad. I liked how it incorporated ideas from FORTRAN, ALGOL, and
COBOL. My student job was to enhance a PL/I package for a History professor.
What language were the PL/I compilers written in?
The only PL/I compiler I have access to is, somewhat ironically, the Multics PL/1 compiler. It is largely self-hosting; more details can be found here: https://multicians.org/pl1.html
(Note Doug's name appears prominently.)
Wikipedia claims that IBM is still developing a PL/I compiler, which I suppose I have no reason to disbelieve, but I'm very curious as to who is using it and for what purpose.
I imagine most of it is legacy code in a mainframe environment, similarly to COBOL. I can't imagine that many folks are considering new development in PL/1 other than in retro/hobbyist environments and some mainframe shops where there's a heavy existing PL/I investment.
- Dan C.