[userbinator]

Hydraulic relays? I vaguely remember coming across a similar "bottom-up" book about how computers work many decades ago (near the end of the mainframe/minicomputer era) which used water flowing through pipes and valves as its analogy. Unfortunately the title wasn't so memorable, but I do recall the cover was a photo of a little girl filling a bucket from a spigot on the outside of a house. Does anyone know what book that was? I've searched a bit before, but had no luck.