Following the Joe Armstrong quotes, there is one about the print statements.

Seibel: What are the techniques that you use there? Print statements?

Armstrong: Print statements. The great gods of programming said, “Thou shalt put printf statements in your program at the point where you think it’s gone wrong, recompile, and run it.”

Then there’s—I don’t know if I read it somewhere or if I invented it myself—Joe’s Law of Debugging, which is that all errors will be plus/minus three statements of the place you last changed the program. When I worked at the Swedish Space Corporation my boss was a hardware guy. We were up at Esrange, the rocket-launching site and satellite-tracking station in the north. And one time he was banging his head, debugging some bug in the hardware, plugging in oscilloscopes, and changing things. And I said, “Oh, can I help?” And he said, “No Joe, you can’t help here—this is hardware.” And I said, “Yeah, but it must be like software—the bug will be pretty near to the last change you made to the hardware.” And he went, “I changed a capacitor. You’re a genius!” He’d replaced one capacitor with a bigger capacitor and he unsoldered it and put the original one back and it worked. It’s the same everywhere. You fix your car and it goes wrong—it’s the last thing you did. You changed something—you just have to remember what it was. It’s true with everything.

Coders at Work – Page 227 – Joe Armstrong

This quote is interesting because there is such an amount of information in the internet about that. Debugging Vs Print statements has evolve since the time’s Armstrong made his debut in the professional programming world.

Another interesting content about debugging, more related at the state of the art in the first half of the twenty-first century maybe this video of IBM: