The choice of an implementation language is somewhat less clear cut. The most obvious contender would be C  in conjunction with the Xlib library. However, it was deemed that this library was too low-level for rapid application development. Another possibility was the use of C++  and the Fresco class library. While it is higher level than Xlib and shows great promise, it still represents, at the time of writing, a work in progress; hence, its potential usability and stability is questionable. InterViews , the forerunner of Fresco, was another considered as another possible option; however, support for this class library appears to have been abandoned in favour of Fresco. Finally, a scripting language known as Tcl/Tk  was evaluated and eventually chosen as the desired implementation language.
Tcl (Tool Command Language) is a simple scripting language that is being developed by Sun Microsystems which provides support for common programming concepts such as variables, control flow, procedures and string manipulation. Tcl scripts can be used either as a stand-alone language or they may also be embedded in C code, thereby interfacing with existing libraries and legacy code. Tk (Toolkit) is an extension of Tcl which can be used for implementing graphical user interfaces for the X Window System. Tk provides the programmer with a wide variety of widgets (such as buttons, listboxes, canvases and scrollbars) which can be configured and arranged in a flexible manner to build a robust GUI.