Subsection 29.1.3 ActiveCode Programming Windows
A window that allows for entering, and executing, computer programs can be made available for every page. The reader can click on a pencil icon to activate this window. Some languages can run in a web browser as part of any HTML output, while some other languages require infrastructure on a Runestone server to execute, and so are only available when you specify that hosting option. Note that the publisher will select a single language for use with the entire document. See Subsection 44.4.5 for details on specifying this option.