The identification of pens serves to emphasizing parts of the picture drawn with the same pen and to informing about the number of pens used during drawing the given picture. This information is useful namely for the correct loading of the plotter pens in case you decide to draw the given picture on the plotter.
The following conditions must be accomplished if you want to emphasize a part of the picture drawn with the same pen:
1) the installed Windows video driver must support a logical palette (usually a Super VGA video driver for a 256 colors mode),
2) the number of items in the logical palette must be at least equal to maximal number of plotter pens (note that for VGA 256 color mode the number of items in logical palette is only 236 because of 20 reserved system colors).
3) the used plotter driver must not support and use the PC (Pen Color) instruction (note that the PC instruction is currently supported only by driver for HP-GL/2 raster device and this support can be disabled).
4) the Use Logical Palette item in the Preferences dialog must be checked and must not be disabled (it is disabled if the logical palette is not supported by your video driver or it is not large enough to be used in any way),
Then if you click on the desired Pen Icon on the Pen Panel, a part of the picture drawn by the corresponding pen will begin to flash and it will be flashing until you click another pen icon or if you do not cancel the identification by clicking the same pen icon. Note that a double-click on a pen icon invokes the Pen Colors dialog for editing of the corresponding pen color.
The another purpose of the Pen Panel is to identify the numbers of pens used during drawing the picture. At the beginning of drawing all the pen numbers are grayed, during drawing the number corresponding with the pen just being used is highlighted, after finishing drawing all the numbers corresponding with all the used pens are highlighted so that all the unused pen numbers remain grayed.