SHRDLU was a ground-breaking AI program written in the early 1970s by Terry Winograd at MIT. The name SHRDLU is derived from ETAOIN SHRDLU, a traditional phrase entered by hot-metal typesetters to indicate the end of a newspaper story. SHRDLU tested theories of natural language processing and problem solving. The user would type in English requests to manipulate a set of building blocks on the screen. One could ask questions about the the microworld and the computer would reply. It was a natural language interface for block stackers.