XPvmode()
  Get and Set the video mode
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   Function:   XPvmode()

               This function provides some control over the
               Video mode. Using XPvmode() one can check the
               current state of the Video Mode, and eventually
               set the Video Mode.
               This can be handy to set alternative video modes

               Note that the MaxRow()/MaxCol() and other Terminal
               settings are not affected. It's a pity that the
               Terminal system is not documented. This function is
               thus particurlarly handy to enquire about the
               current mode, or reset after a graphics mode.

   Syntax:     XPvmode([<nMode>])

   Arguments:  <nMode> can be given, which will tell XPvmode() to
               set the specified Mode.

   Returns:    The current Video Mode, That is, The Mode *before*
               any eventual other Mode that will be set if a
               parameter is given to XPvmode().

   Usage:      Useful for returning from graphics mode..
               See the XPfastPCX() function.