XML (Extensible Markup Language) has become state of the art to store data. It contains data including type and hierarchal structure. Since this mostly this overhead to structure the data can take more disk space than the the data itself, many formats use XML and zip it when it is saved to memory. Examples are OpenOffice, Microsoft Words docx, Epub,.... . To test it rename the file to have the .zip extension and then unzip it. XML is usually read from a file but it can also read from any communication data stream.

Unfortunately a lot of terms need to be understood before not getting lost with XML. Documents are mostly written very confusing instead to explain the concept by simple words. Often reverse engineering is the quicker approach.

To use XML a editor with syntax highlighting and oder xml functions is a must. Tools are xmlcopyeditor or the simple XML editor qxmledit, that can be started as QXmlEdit.

The first line of a xml should be something like this, that defines that it is an xml document following version 1.0:

<?xml version="1.0"?>

More clean is to add the character encoding as well

<?xml version="1.0" encoding="UTF-8"?>