GTK+ is a C based toolkit for programming graphical applications in X windows. It is highly object oriented and has bindings to many popular languages, such as C++, Objective C, Perl, TOM, Guile, Python, etc ... GTK+ also uses GLib, which is a very useful C library, and includes things to help porting to different architectures, and containers such as a linked list or a hash. If you are already familiar with GTK+, you are now free to get bored.