SHRDLU is a program for understanding natural language, written by Terry Winograd 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).
SHRDLU is described in Winograd’s dissertation, which was issued as MIT AI Technical Report 235, February 1971 with the title Procedures as a Representation for Data in a Computer Program for Understanding Natural Language It was published as a full issue of the journal Cognitive Psychology Vol. 3 No 1, 1972, and as a book, Understanding Natural Language (Academic Press, 1972).
SHRDLU was written in MacLisp for the ITS system, vintage 1970. The source code is available at http://hci.stanford.edu/winograd/shrdlu/code and as a TAR file at http://hci.stanford.edu/winograd/shrdlu/code.tar .A discussion of various efforts is on the SHRDLU is at http://www.semaphorecorp.com/misc/shrdlu.html
You can download a Windows text-only console version of SHRDLU implemented in Common Lisp, or a graphical 3-D version implemented with an extra Java layer. Source code is included. These files were supplied by Greg Sharp, and were produced by the UMR student project to resurrect SHRDLU. Double-click the SHRDLU.BAT file in either version to start running. No guarantees.