ABSTRACT
Parallel or concurrent operation has many different forms within a computer system. Multiple computers can be executing pieces of the same program in parallel, or a single computer can be executing multiple instructions in parallel, or some combination of the two. Parallelism can arise at a number of levels: task level, instruction level, or some lower machine level. The parallelism may be exhibited in space with multiple independently functioning units, or in time, where a single function unit is many times faster than several instruction-issuing units. This chapter attempts to remove some of the complexity regarding parallel architectures (unfortunately, there is no hope of removing the complexity of programming some of these architectures, but that is another matter).
