Energy dissipation by a light or electron beam inside a specimen is the primary parameter responsible for generating signals used to characterize the sample under investigation. The commonly used semi-empirical descriptions of this energy dissipation profile are presented. Their limitations in dealing with particular experimental conditions, such as multi-layer specimens and varying beam tilt angles, make it necessary to evaluate the beam-matter interaction parameters by methods such as Monte Carlo simulations. The physical principles of these simulations are introduced along with the presentation of computational details of a fast calculation program developed by the author, in particular for dealing with the evaluation of energy deposition. Some of the applications of calculated energy dissipation profiles and other data calculated in the beam induced assessment of device properties are outlined, along with examples comparing simulation results to experimental data.