xnec2c is a GTK+ graphical interactive version of nec2c. It incorporates the nec2c core which it uses for reading input files and calculating output data, but it does not need and indeed does not produce an output file by default. Since xnec2c incorporates the nec2c core, it has access to all internal buffers, including structure data, frequency-related data (structure currents, input impedance, gain etc) and radiation pattern data (for the far field and near field). It therefore has the ability to graphically display user-requested data directly, as the frequency loop progresses or after input from the user. Graphs of frequency-related data and the current or charge distribution evolve as the frequency loop progresses, and radiation patterns (far and near field) are sequentially drawn for each frequency step. A new frequency can be entered by the user from spin buttons in the main or radiation pattern windows or by clicking on the graphs of frequency-related data. New output data are then computed and displayed in text and graphical form.