The GPORT subroutine is a graphical call that defines a viewport. The rectangular area’s boundary is specified in normalized coordinates, where you specify the coordinates of the lower left corner and the upper right corner of the rectangular area in the form

The GPORT subroutine changes the current viewport. The viewport argument defines the new viewport by using device coordinates (always 0 to 100). Changing the viewport can affect the height of the character fonts; if so, you might want to modify the HEIGHT parameter. An example of a valid statement follows:

call gport({20 20 80 80});

The default values for viewport are 0 0 100 100.