By denition, supercomputers are the fastest and most powerful computers available, and at
present the term refers to machines with hundreds of thousands of processors. They are the super-
stars of the high{performance class of computers. Personal computers (PCs) small enough in size
and cost to be used by an individual, yet powerful enough for advanced scientic and engineering
applications, can also be high{performance computers. We dene high{performance computers as
machines with a good balance among the following major elements: