## 2.1.1 Previewing graphs on the screen

Three output terminal produce immediate previews to the screen: `X11_singleWindow`, `X11_persist`, `X11_multiWindow`. The default of these options – i.e. the default terminal when Pyxplot is started up in interactive mode – is `X11_singleWindow`. In this terminal, each time a new plot is generated, if the previous plot is still open on the display, the old plot is replaced with the new one. This way, only one plot window is open at any one time. This behaviour is intended to prevent the desktop from becoming flooded with plot windows.

The alternative `X11_multiWindow` terminal is similar in all respects except that each new plot is generated in a new window, regardless of whether any previous plots are still open on the display. This is especially useful when multiple plots are to be compared side-by-side:

    set terminal X11_singleWindow
    plot 'data1.dat'
    plot 'data2.dat'  <-- first plot window disappears

c.f.:

    set terminal X11_multiWindow
    plot 'data1.dat'
    plot 'data2.dat'  <-- first plot window remains

The third of these terminals, `X11_persist`, is similar to `X11_multiWindow` but keeps plot windows open after Pyxplot terminates in distinction from the above two terminals, which close all plot windows upon exit.