Apart from boundary condition files that are controlled by individual modules, restart file input and output is controlled by IORSF. This is a driver routine that calls individual io_XYZ routines for each module. This allows different versions of each module to control the I/O of the required prognostic variables. Depending on the value of iaction in the call, different kinds of I/O can be set (read or write, double or single precision, with or without tracers, with diagnostics or not).