This library gathers a few functions used by a set of monitors e.g. Monitor_nD, Res_monitor, etc. It is also used by Virtual_output, a code-specific event-file writer that has moved to the obsolete component category (see the Component Manual’s Obsolete chapter) and is superseded by MCPL_output; new instrument work should prefer MCPL. It may monitor any kind of data, create the data files, and may display many geometries (for mcdisplay). Refer to these components for implementation examples, and ask the authors for more details.