dual monitor in macbook pro.

there are two modes: one is the extend the desktop on the external monitor, and the second is using the same desktop or mirror desktop.  The mode can be chosen in the 

system preference --> display --> arrangement tab,

then check the mirror displays option or deselect the option.

Command-F1 to toggle between mirrored and extended desktop modes.  Ctrl-Alt-Command-8 to toggle ‘white on black’ display in low-light situations. (Command-Alt-8 will also toggle zooming). But those who really want to get to know their laptop keyboards will want to look at this 15-inch PowerBook G4 Developer Note, which is still mostly applicable to MacBooks.

http://the.taoofmac.com/space/HOWTO/Switch%20To%20The%20Mac