Abstract: A shared storage multiprocessing system in which storage is arranged into blocks of storage for storing blocks of data and in which prefixed storage areas for the processors are assigned to predetermined blocks of storage in accordance with different prefix numbers having predetermined values with at least one prefixed storage area being assigned to the zero block of storage. Each of the processors includes a control register which provides the prefix number, an addressing means which provides reference block addresses and prefix logic means which selectively responds to the value of the prefix number and the values of the reference block addresses to provide storage block addresses for addressing the blocks of data in storage.