ACTIVIA: Calculation of Isotope Production Cross-sections and Yields

We present a C++ computer package, ACTIVIA, that can calculate target-product cross-sections and the production and decay yields of isotopes from cosmic ray activation using data tables and semi-empirical formulae. We describe the structure and user interface of the computer code as well as provide comparisons between the calculations and experimental results. We also outline suggestions on how the code can be improved and extended for other applications.