Question: In practically every computer I’ve had, there’s always been a light to display hard drive activity. What’s its origin and original use?
Answer: Well, I can say, as an engineer for MiniScribe (later Maxtor), it’s exactly what it appears to be. It’s an “activity” light. It was a way for us to tell that a command had been received through the interface and was underway. It was a debugging tool for those of us who, you know, built disk drives.