This command logically takes the picture variable specified, and takes the current graph, and it finds the points at which only the graph or only the picture have pixels, but turns off the points at which both have pixels, and it displays them only. If specified, [row,column] tells where the top left corner of the picture is to be placed. If not specified, the default is (0,0), which is the top left corner of the screen.
260 - Domain error happens when the [row][,column] argument is outside the screen range..
960 - Undefined variable happens when the picture variable specified does not exist..