SHRDLU is a program for understanding NaturalLanguage, written by TerryWinograd at the M.I.T. Artificial Intelligence Laboratory in 1968-70. SHRDLU carried on a simple dialog (via teletype) with a user, about a small world of objects (the BLOCKS world) shown on an early display screen (DEC-340 attached to a PDP-6 computer).
See http://hci.stanford.edu/~winograd/shrdlu/
Also see GeneralProblemSolver.
SHRDLU was featured in GoedelEscherBach.