A class of very powerful computers that have extremely fast processors, currently capable (2008) of performing several hundred Tflops, i.e. 1012 floating-point operations per second (see flops); most are now multiprocessor systems (see also SMP, MPP). Large main-memory capacity and long word lengths are the other main characteristics. Modern supercomputers are also created from large numbers of standard microprocessor chips operating in parallel. Supercomputers are used, for example, in meteorology, engineering, nuclear physics, and astronomy. Several hundred are in operation worldwide at present. Principal manufacturers are Cray Research, IBM, NEC, and Fujitsu.