Yep. I have recently used prompts to ask for COBOL code solution so I can compare it to other languages I also know to check quality of the answer. So far no mistakes.

I'm sure they can do brainfuck if you have a good training set.

> Can LLMs do Cobol?

I imagine it's the one place where LLMs would absolutely shine. COBOL jobs are usually very verbose, lots of boilerplate, but what they do is mostly very straightforward batch processing. It's ripe for automation with LLMs.

The flip side is that banks are usually very conservative about technology (for good reason).

Yes! But only if they write the compiler too.