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The authors are developing a series of special-purpose computers, GRAPE (GRAvity PipE), for simulations of many-body systems such as star clusters and systems of molecules. In simulations of many-body systems, almost all the computing time is consumed in the calculation of the force between the particles. A host computer sends the positions of the particles to GRAPE, which then calculates the force exerted on a particle and sends it back to the host computer. The host updates the positions, velocities, etc., of the particles. The machines with odd numbers (GRAPE-1, GRAPE-1A, GRAPE-3, and GRAPE-3A) belong to the low-accuracy type. The machines with even numbers (GRAPE-2 and GRAPE-2A) belong to the high-accuracy type. GRAPE-2A was designed for the application of molecular dynamics simulations as well as gravitational many-body simulations. The computational speed of GRAPE-2A is about 180 MFLOPS. The authors are designed a highly parallel machine, GRAPE-4, in which many GRAPE pipelines work in parallel.