ET++ is a portable and homogenous object-oriented class library integrating user interface building blocks, basic data structures, and high level application framework components. ET++ eases the building of highly interactive applications with consistent user interfaces following the direct manipulation principle. The ET++ class library is implemented in C++ and can be used on several operating systems and window system platforms. Since its initial conception the class library has been continuously redesigned and improved. It started with an architecture which was close to MacApp. During several iterations a new and unique architecture evolved. A byproduct of the ET++ project is a set of tools, which were designed to support the exploration of ET++ applications at run-time. 設計模式一書引用的主要參考例程，一個跨平臺的應用框架，基于C++實現，是學習面向對象的經典源碼.
