parallel processing, the concurrent or simultaneous execution of two or more parts of a single computer program, at speeds far exceeding those of a conventional computer. Parallel processing requires two or more interconnected processors, each of which executes a portion of the task; some supercomputer parallel-processing systems have hundreds of thousands of microprocessors. The processors access data through shared memory. The efficiency of parallel processing is dependent upon the development of programming languages that optimize the division of the tasks among the processors.