  Thin film technology is a most relevant field in terms of number of different
applications and, even more, in how widespread the use of the technology is.
Virtually all optical devices involving light beams or with imaging
capabilities available on the market contain thin film assemblies that are
crucial for enhancing the practical performances of the device. So, nowadays,
thin film coatings are routinely deposited on very different kinds of
substrates. From the beginning, the use of thin films required the optical
characterization of the coating materials as well as the design of the suitable
thin film structures in order to meet the optical requirements. This has been a
significant research topic in the past but the impact of high level programming
languages has dramatically changed the scenario. Nowadays, to address the more
advanced computation tasks related to thin film technology is much simple. The
aim of the Tutorial presented here is to enable the reader (with only a basic
knowledge of the use of Matlab or Python) to perform advanced numerical
computations of the optical properties of thin film structures. We will explain
the necessary steps and supply the corresponding program codes, with complete
comments. For conciseness, our short theoretical introduction will follow the
scheme established elsewhere and we will concentrate on developing in detail
several practical examples of increasing difficulty, so that understanding and
using the Tutorial becomes entirely intuitive.
