The program keeps in memory up to 19 different data sets in a stack, these data sets are called ``buffers''. The up-to-date buffer, the last one, usually displayed on screen, is #10.
Modifying a buffer (doing any transformation described here) causes the last ten buffers to move upwards in the stack (then the old 10th buffer becomes the 11th etc...), while the transformed buffer takes rank #10.
This allows the Undo commands (which moves all the buffers downwards), the Redo commands (which moves all the buffers upwards), and the sWitch command which moves any buffer to the 10th position.
Note that you could use the Undo/Redo without caring about how it works ! The large number of Undo/Redo makes it possible to analyze different regions of a data set without having to load the same file twice.
The entire stack can be saved with the command savestack, or loaded with the command...loadstack.
The overlay commands allow you to plot two buffers at once. If you want to overlay more data sets, you can mark all the buffers you want to superimpose. See the mark commands
Christophe Leger 2009-02-24