I had some colleagues who had worked on mainframe operating systems tailored for the airlines (PARS), and it's built upon TPF as I understand it. I don't know w

I had some colleagues who had worked on mainframe operating systems tailored for the airlines (PARS), and it's built upon TPF as I understand it. I don't know which language(s) it's implemented in, but I do recall them talking about assembler having a major role.