Command entry:Click or right-click the Point-Of-View (POV) viewport label. 
POV viewport label menu Choose Perspective or Orthographic. You can also choose a specific orthographic view such as Front, Top, Left, Right, and
so on.
Command entry:Click or right-click the Point-Of-View (POV) viewport label. POV viewport label menu Grid Grid submenu Choose a grid view.
Command entry:Select a shape. Click or right-click the Point-Of-View (POV) viewport label. POV viewport label menu Shape
Perspective, orthographic, user, grid, and shape viewports all share the same viewport controls.
Perspective and orthographic viewport controls include the following. Two of these controls are available in all viewports.
Zoom Extents / Zoom Extents Selected (available in all viewports)
Orbit, Orbit Selected, Orbit Sub-Object
Maximize Viewport Toggle (available in all viewports)
To undo changes to a Perspective or orthographic viewport, do one of the following:
When Zoom is active, you can adjust the view magnification by dragging in a Perspective or orthographic viewport. By default, zooming occurs from the center of the viewport.
Zoom All lets you adjust view magnification in all Perspective and orthographic viewports at the same time.
The Zoom Extents flyout displays the Zoom Extents button and the Zoom Extents Selected button.
The Field Of View flyout is available only for Perspective viewports. It lets you change the field of view, or zoom to a particular region.
Field-of-View (FOV) adjusts the amount of the scene that is visible in a viewport and the amount of perspective flare. The effect of changing FOV is similar to changing the lens on a camera.
Zoom Region magnifies a rectangular area you drag within a viewport. This control is available only when the active viewport is an orthographic, Perspective or User-Axonometric view. It is not available for Camera viewports.
Pan moves the view parallel to the current viewport plane.
The Orbit flyout contains the Orbit, Orbit Selected, and Orbit Sub-Object buttons.