In the paper, the authors solve parametric linear systems of equations whose co-efficient are, in the general case, non-linear functions of interval parameters. Here, solution means that they enclose the set of all solutions, the so-called parametric solution set, obtained when all parameters are allowed to vary within their intervals. This task appears in many scientific and engineering problems involving uncertainties. A C-XSC implementation of a parametric fixed-point iteration method for computing an outer enclosure for the solution set is proposed in this paper.