To run a single trajectory, the user should provide dynamics parameters defining the methods to be used and the initial conditions, including the molecular initial state L. Newton-X calls third-party quantum-chemical programs to compute electronic energies (E), energy gradients (g), and, optionally, either nonadiabatic coupling vectors (h) or atomic orbital overlaps between different time steps (s). The latter is employed to build the wavefunction overlap matrix S for either time-derivative couplings or local diabatization (LD). All this information comes together to propagate classical and quantum equations of motion (EOM) in one timestep. The fewest-switches surface hopping (FSSH) is used to determine the electronic state L for the new time step.