Mini DisplayPort output port with support for DVI, VGA and dual-link DVI (adapters sold separately). 27-inch models also support input from external DisplayPort sources (adapters sold separately).
Mini DisplayPort. The Mini DisplayPort lets you connect an external display, including the Apple LED Cinema Display, to your iMac. On the 27-inch iMac, the same port offers input, too. So you can connect any external source that has DisplayPort output — including a MacBook or MacBook Pro — and use your iMac as a display.