The scale of a window's contents can be controlled in a number of ways. The Zoom In command (in menu Window) zooms in, magnifying the contents of the display. The Zoom Out command does the opposite - it shrinks the display. Both zoom by a factor of two.

During normal editing, you can zoom the display with the shift-right button or with the control-mouse-wheel (see Section 1-8). Holding shift-right while dragging a rectangular area causes the display to zoom into that area, making it fill the screen. Clicking shift-right in a single location causes the display to zoom out, centered at that point. Holding the control key and rolling the mouse wheel also zooms in and out.

| You can also use the Zoom tool from the tool bar to zoom in and out. This has the same zoom in and out functions, but they are now attached to the left button (no shift needed). To zoom into an area, click and drag out that area. To zoom out, hold the shift key and click in the center of the desired area. The Zoom tool can also scale continuously by clicking the right button and dragging up and down. This mode can also be invoked with the Toggle Zoom command (in menu Edit / Modes / Edit).

The most useful scale change command is Fill Window (in menu Window), which makes the current cell fill the window.

There are four special zooming commands in the Window / Special Zoom menu:

- Focus on Highlighted makes the highlighted objects fill the display. This is useful for examining a specific area of the display. To examine a specific area of the display that is not necessarily aligned with nodes and arcs, use the area select commands (see Section 2-1-3).
- Zoom Box allows you to drag-out a rectangle, and then zooms to that area.
- Make Grid Just Visible zooms in or out until the grid is minimally visible. Any further zoom-out from this point will make the grid invisible. If the grid is not being displayed, it is turned on. See Section 4-7-1 for more on the grid.
- Match Other Window redraws the current window at the same scale as the other. If there are more than two windows, you will be asked to select the window to match.