for some ideal "I" in "S". The complements of these closed sets define a topology on Proj "S". The ring "S", by localization at a prime ideal, determines a sheaf of local rings on Proj "S". The space Proj "S", together with its topology and sheaf of local rings, is a scheme. The subset of closed points of Proj "S" is homeomorphic to CP"n" with its Zariski topology. Local sections of the sheaf are identified with the rational functions of total degree zero on CP"n".