Unless a file is listed in overlays.txt , however, it will not be available to the system. Overlays include simple graphics. The polyline is terminated as usual, by a blank line or a command line. Text requires a quoted string as its third argument, but that string may include blanks. It may be quoted with either single or double quotes.
Some commands influence how future primitives are drawn.
They will be drawn 2 pixels to the right and down from the overlay object, in black. The first is the number of sides in the object to be drawn. This number is a non-negative integer. If it is zero, the marker will be a circle. 1 and 2 usually produce unattractive markers.