xconfig is short for the 'xconfig' target for the Linux

Linux kernel

The Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....

 Makefile. It is a graphical Linux compilation utility, which uses Qt

Qt (toolkit)

Qt is a cross-platform application framework that is widely used for developing application software with a graphical user interface , and also used for developing non-GUI programs such as command-line tools and consoles for servers...

. The xconfig utility is invoked by running 'make xconfig' in the base Linux source directory.

Qt has only been used in Kernel 2.6. Kernel 2.4 uses a Tcl

Tcl

Tcl is a scripting language created by John Ousterhout. Originally "born out of frustration", according to the author, with programmers devising their own languages intended to be embedded into applications, Tcl gained acceptance on its own...

/Tk configuration interface. A GTK+

GTK+

GTK+ is a cross-platform widget toolkit for creating graphical user interfaces. It is licensed under the terms of the GNU LGPL, allowing both free and proprietary software to use it. It is one of the most popular toolkits for the X Window System, along with Qt.The name GTK+ originates from GTK;...

interface is also available for Kernel 2.6.