You've learned in a previous tutorial that the master file for a screenbook is a file named sbook.xml in the screenbook folder. All of the HTML files for a screenbook are created from this master file.

The process goes likes this:

When you click on the Finish button when editing a screenbook, Screenbook Maker saves the text of the screenbook, and links to the PNG files, into sbook.xml.

Screenbook Maker then looks in the bookshelf file for files beginning with sbx_ and ending with .xsl. These files are XSLT files. XSLT is a language that contains instructions for transforming XML (like the contents of sbooks.xml) into HTML or another format.

For each and every XSLT file that Screenbook Maker finds in the given bookshelf, Screenbook Maker transforms sbook.xml and stores the resulting output in a file with the same name as the XSLT file, but without the sbx_ prefix, and the .xsl suffix. If there is no other suffix in the resulting file name, Screenbook Maker adds the suffix .htm.