The GSET('TRANSNO',
. . . ) function activates the viewport, or the window that you have
defined for the specified transformation number, or both. If you have
not defined both a viewport and window for a transformation, the default
is used for the one missing.
You can select 0 as
the active transformation, but you cannot define a viewport or window
for that transformation number. A transformation of 0 activates the
default viewport, (0,0) to (1,1), and window, which is device dependent.