Physical Processes in the Interstellar Medium.- Introduction.- Composition of the ISM.- Heating and cooling of interstellar gas.- ISM Turbulence.- Formation of molecular clouds.- Star Formation.- Summary.- High performance computing and numerical modelling.- Preamble.- Collisionless N-Body dynamics.- Time Integration techniques.- Gravitationals force calculation.- Basic gas dynamics.- Eularian hydrodynamics.- Smoothed particle hydrodynamics.- Moving-mesh...