I would love to hear about the programming languages that I have never heard about. I don't mean Assembly or anything that is low-level, but mainstream. Even better if you have an example!
I would not be surprised if TAL is still used for <a href="https://www.hpe.com/us/en/servers/nonstop.html" rel="nofollow">https://www.hpe.com/us/en/servers/nonstop.html</a> boxen.<p>Similarly, <a href="https://www.unisys.com/client-education/clearpath-forward-libra-servers/" rel="nofollow">https://www.unisys.com/client-education/clearpath-forward-li...</a> probably still uses its bespoke languages ( <a href="https://en.wikipedia.org/wiki/Burroughs_Large_Systems#ALGOL" rel="nofollow">https://en.wikipedia.org/wiki/Burroughs_Large_Systems#ALGOL</a> ) in places.
Do you have any interest in academic languages?<p>After a half a century or so without, BCPL recently got floats (for a flight simulator): <a href="https://www.cl.cam.ac.uk/~mr10/BCPL.html" rel="nofollow">https://www.cl.cam.ac.uk/~mr10/BCPL.html</a><p>I prefer the author's MCPL: <a href="https://www.cl.cam.ac.uk/~mr10/MCPL.html" rel="nofollow">https://www.cl.cam.ac.uk/~mr10/MCPL.html</a> but have no idea if anyone is currently using it.<p>[Edit: looks like Martin backported pattern matching from MCPL into BCPL ca. Oct 2022, so that's recent signs of life for both strains!]
JScript is Microsoft's JavaScript that can run server side. I guess it was a thing in the late 90s and early 00s. The "Click Commerce" web CMS/framework was largely written in it. They pivoted from commerce to medical research, and the software is still being used by dozens of institutions.