The GPORTSTK subroutine is a graphical call that stacks the viewport defined by the matrix viewport onto the current viewport; that is, the new viewport is defined relative to the current viewport. The viewport argument is a numeric matrix or literal defined in normalized coordinates of the form

{minimum-x minimum-y maximum-x maximum-y}

This graphics command uses world coordinates. An example of a valid statement follows:

call gportstk({5 5 95 95});