Trivia note: the IBM PL/I (F) compiler, circa mid60s, used OS calls to allocate and free stack frames on entry/exit of each procedure. My guess is that they did

Trivia note: the IBM PL/I (F) compiler, circa mid60s, used OS calls to allocate and free stack frames on entry/exit of each procedure. My guess is that they did this because they were trying to implement concurrency (TASKs), and threads were not yet understood. As a result, the Programmer's Guide has the following tip: “Do not use procedures; they are expensive.” I would hazard a guess that later PL/I compilers did this better.