The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do.

Ted Nelson, a pioneer of hypertext and an early critic of simplistic views of computing, used this aphorism in the milieu of late‑20th‑century programming culture, where “computer errors” were increasingly understood as human instruction errors. The line is typically invoked in discussions of programming, debugging, and human–computer interaction to stress that computers execute instructions literally and relentlessly. It reflects a period when personal computing and software development were becoming mainstream, and when the gap between what users intend and what they actually specify (in code, commands, or interfaces) was a central practical and philosophical problem in computing.

Nelson’s quip captures a central paradox of computing: machines are perfectly obedient, which is both their power and their danger. Computers reliably execute instructions without judgment, context, or common sense; they do not “know what you meant,” only what you specified. This makes automation possible at scale, but it also means that vague requirements, hidden assumptions, or small errors can be amplified into major failures. The line also points to a broader human-computer relationship: responsibility for outcomes ultimately rests with the people who design, program, and deploy systems. In that sense, the quote is an early, memorable warning about precision, testing, and accountability in software.

1) “The nice thing about computers is that they do what you tell them to do. The bad thing is that they do what you tell them to do.”
2) “The good thing about computers is that they do what you tell them; the bad thing is that they do what you tell them.”