Flynn's taxonomy is a classification of computer architectures, proposed by Michael J. Flynn in 1966[1] and extended in 1972.[2] The classification system has stuck, and it has been used as a tool in the design of modern processors and their functionalities. Since the rise of multiprocessing central processing units (CPUs), a multiprogramming context has evolved as an extension of the classification system. Vector processing, covered by Duncan's taxonomy,[3] is missing from Flynn's work because the Cray-1 was released in 1977: Flynn's second paper was published in 1972.