/siks dub*l oh wun/, /dub*l oh wun/ or rarely /siks dub*l oh fun/ mit's introductory computer class for majors, known for its intensity. Developed by gerald sussman and hal abelson, the course is taught in scheme and introduces recursion, higher-order functions, object-oriented programming and much more. Students who grasp the metacircular interpreter gain entry into the knights of the lambda-calculus. 6.001 has been exported to several other colleges, sometimes successfully. The textbook, "Structure and Interpretation of Computer Programs", written with Julie Sussman is a classic that can be found on the shelves of many computer scientists, whether they took the course or not. Legendary characters from the class, problem sets, and book include the wise Alyssa P. Hacker, Ben Bitdiddle, Lem E. Tweakit and Eva Lu Ator, the careless Louis Reasoner and captain abstraction.