PrintWe already mentioned a few things about QT in this lesson. It is a widely used cross-platform library written in C++, modern and under very active development. In addition to the GUI functionality, the library provides support for internationalization, Unicode, database and network access, XML and JSON code processing, thread management, and more. That’s why it is also called an application framework, not just a GUI library. QT was originally developed by the company Trolltech and its initial release was in 1995. KDE, one of the early GUIs for the Linux operating system, was based on QT and that triggered a lot of discussion and changes to the license and organization QT was published under. These days, the company developing QT is called The QT Company, a successor of Trolltech, and QT is published in four different editions, including the Community edition that is available under different open source licenses GPL 3.0, LGPL 3.0, and LPGL 2.1 with a special QT exception. QT is very commonly used for both open source and commercial software, and if you have worked with QT in one programming language, it is typically relatively easy to learn to use it in a different language. QT5 was released in 2012 and the current version of QT at the time of this writing is 5.10.