Highlight from The Clean Coder: A Code of Conduct for Professional Programmers

Nowadays, of course, we'd use the plethora of powerful tools at our disposal to find all the places where the code touched those variables. Within seconds we'd know every line of code that touched them. Within minutes we'd know which did not disable the interrupts. But this was 1972, and I didn't have any tools like that. What I had were my eyes.