Isolated and Interacting Galaxies : Simulations with GRAPE

12 pages, 9 figures, includes iau208.sty and iau208_epsf.tex, review paper for IAU Symp. 208, Astrophysical Supercomputing using Particles, eds. J. Makino & P. HutI present N-body simulations of isolated and interacting galaxies, made on GRAPE machines. In particular I discuss the formation and evolution of N-body bars and compare their properties to those of bars in early-type and late-type galactic discs. I argue that the halo can help the bar grow, contrary to previous beliefs, by taking positive angular momentum from it via its resonant stars. I then focus on the interaction and subsequent merging of a barred disc galaxy with a spheroidal satellite. The evolution depends strongly on the mass (density) of the satellite and may lead to its destruction or to the destruction of the bar