When more than one monitor is connected to your computer, the desktop area can be extended to create a larger work area. To use this feature, your computer must generally have two or more video cards installed. (Some Apple computers can work with two monitors without requiring an additional video card. Check the documentation that came with your computer.)
The Mac OS automatically recognizes when two or more monitors are connected to the computer. You can choose which monitor has the menu bar, and you can arrange the logical desktop space to match the physical placement of the monitors (which one is on the left or right, for example).
To make these settings:
1. Open the Monitors control panel (Mac OS 9) or the Displays pane of System Preferences (Mac OS X).
2. Click Arrange.
3. Follow the on-screen instructions.
Figure 1 Mac OS 9 Monitors control panel
Figure 2 Mac OS X Displays pane of System Preferences
Video mirroring
The video mirroring feature allows you to see the same screen on two different monitors. This is particularly useful in a classroom or presentation setting where you need to be in front of an audience that is watching one screen, and you are watching the other.
To use this feature, your computer must generally have two or more video cards installed. (Some Apple computers can work with two monitors without requiring an additional video card. Check the documentation that came with your computer.)
In Mac OS 9, choose Turn Video Mirroring On from the Video Mirroring portion of the Control Strip.
Figure 3 Video Mirroring portion of the Control Strip
Follow these steps to turn on video mirroring in Mac OS X:
1. Open System Preferences.
2. Click Displays.
3. Click the Arrange tab (if necessary).
4. Click Mirror Displays to enable this option.