The CUDD package provides functions to manipulate Binary Decision Diagrams (BDDs) [5,3], Algebraic Decision Diagrams (ADDs) [1], and Zero-suppressed Binary Decision Diagrams (ZDDs) [12]. BDDs are used to represent switching functions; ADDs are used to represent function from to an arbitrary set. ZDDs represent switching functions like BDDs; however, they are much more efficient than BDDs when the functions to be represented are characteristic functions of cube sets, or in general, when the ON-set of the function to be represented is very sparse. They are inferior to BDDs in other cases. The package provides a large set of operations on BDDs, ADDs, and ZDDs, functions to convert BDDs into ADDs or ZDDs and vice versa, and a large assortment of variable reordering methods.