User Fortran using shared libraries is more versatile if its key parameters can be changed between runs without the need for recompilation or maintenance of different versions of the routines.

For example, the same User Fortran source code may be run for different applications or for parametric studies, but each run may need to open a different filename for reference data, or use a different value for some model option or a model parameter. Such parameters may be passed to the User Fortran through the command language in the CFX-Solver input file or the results file. In a parallel run, each partition gets a copy of this data. A demonstration on the use of some user parameters is available in Junction Box Example 1: Profile Boundary Conditions.