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.

nec2c is a C translation of the Fortran nec2 code, which allows analysis
of antennas.