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Binary decision diagrams (BDDs) provide a canonical and compact representation of Boolean functions. The canonical property makes it possible to easily detect many useful properties of Boolean functions such as size of the support set, symmetry between variables etc. Furthermore, BDDs compact representation coupled with the use of data structures for caching intermediate computations allows the effective implementation of many Boolean operations. In this paper, we present a new methodology and implementation details of the composition techniques of two combinational switching functions using reduced ordered binary decision diagrams ROBDDs. For instance, given two switching functions A and B, we present the composition formulas AnlandB,A or B,ArarrB etc using ROBDDs. In this regard, we have used the concept of Shannonpsilas expansion to directly build ROBDDs. An adequate number of examples have been used to make our method clear.