Ages ago, before even dumb terminals, we were programming on punched cards, batch compiling, and printing on a line printer. For some reason, this printer supported control G (the bell character) with a buzzer. So someone hacked the compiler to include control G in the beginning of the error messages.

So we could sit back and listen to the line printer. If the buzzer sounded, the programmer would say "Oh &#$!@". Just like Pavlov demonstrated.