Setting primary and secondary display modes

If I hook up a second display to an iMac then I assume that the iMac's display will be the primary one that will have my dock, icons, etc and the second display will just be free space.

Could I swap that around? Could I made my secondary display the primary one? The reason I ask is that if I do get an iMac I would probably get a 21.5" model but my secondary monitor may be a little bigger, like 24" or so. I'd like to have the bigger monitor be the primary display.

Thanks!

-- Boris

 

Nice! Thanks, that's exactly what I was asking about. It helps me to see this.

-- Boris