We present a detailed description of the features and capabilities of a new software for the optical characterization of thin films from spectrophotometric and/or ellipsometric measurements. The program allows the analysis of a wide range of multi-layered structures, either with respect to the composition, microstructure or thickness of any of the layers. Several spectra corresponding to different measurement techniques of a single sample may be fitted simultaneously. A short description of the dispersion models actually implemented to represent the materials is given. Several examples of use are discussed. These have been selected to illustrate important aspects that may be relevant to microelectronic applications.