XOP v2.4 consists of a collection of computer programs for calculation of radiation characteristics of X-ray sources and their interaction with matter. Many of the programs calculate radiation from undulators and wigglers, but others, such as X-ray tube codes, are also available. The computation of the index of refraction and attenuation coefficients of optical elements using user-selectable databases containing optical constants is an important part of the package for calculation of beam propagation. Coupled computations are thus feasible where the output from one program serves as the input to another program. Recent developments including enhancements to existing programs are described.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.