Figure: Opening screen with energy density and space-time contour plots.
Load and start the program in the same way as other CUPS programs. The
default configuration of a standing electromagnetic wave, shown in
Figure 
, will appear on the screen.
Purple and yellow represent the right- and left- traveling waves, while
the white wave is their sum. The [F2 Run/Pause]
hot key starts and
stops the simulation. Certain hot keys
( [F1 Help],
[F2 Pause], [F3 Offset], [F4 Pos dt], [F5 Faster], [F6 Slower]
)
are accessible while the simulation is running. When the simulation is paused,
you may use the [F7 Reset]
hot key to restore the initial configuration.
The colored boxes in the lower left corner of the bottom graph are buttons that
allow you to create reflectors (r), which reflect specified wave components;
sources (s), which generate a disturbance; segments (n), which simulate
refractive index, potential energy, or diffusivity depending on the
type of simulation; and detectors (d), which monitor wave amplitude.
Simply click once on the button with the label corresponding to the object you wish to
create and click again on the wave graph at the position where you wish to
insert the object.
To zoom in or out on the simulation graph, click the red ``scale" button in the upper left corner of the graph and reset xmin, xmax, ymin, and ymax . Zooming is an option only while the simulation is paused. It changes the display without affecting the data being plotted.
The simulated time after n calculations, 
, is displayed on
screen. Some of the simulations allow the user to reverse time by pressing the
[F4 Pos dt/Neg dt]
hot key. The direction of the time step can also be
changed using the [Parameters]|[Time]
menu. In
addition to letting you ``zero in'' on interesting phenomena, reversing the
time step is a useful check for the accuracy of the algorithm.