An external monitor or projection device connected to the computer can increase the amount of visible desktop space. This way of using an external monitor is called dual display to distinguish it from mirror mode, which shows the same information on both the external display and the built-in display.
When the internal display and an external monitor are both operating and mirror mode is selected, the scaling function is not available. Both displays show full-sized images only when the display resolution for the external monitor is set to the internal display's native resolution: 1280 by 854. Both displays can operate with other resolution settings, but in mirror mode, one of them will have a display that is smaller than the full screen and has a black border around it. With the resolution for the external monitor set to 640 by 480 or 800 by 600, the image on the internal display is smaller than its screen. For resolution settings larger than 1280 by 854, the image on the external monitor is smaller than its screen.