The main input file for an elegant run consists of a series of namelists, which function as commands. Most of the namelists direct elegant to set up to run in a certain way. A few are “action” commands that begin the actual simulation. FORTRAN programmers should note that, unlike FORTRAN namelists, these namelists need not come in a predefined order; elegant is able to detect which namelist is next in the file and react appropriately.