The MacBook Pro replaced the PowerBook G4 and was the second model to be announced in Apple's PowerPC to Intel transition (after the iMac). Positioned at the high end of the MacBook family, the MacBook Pro is currently produced in three sizes: the 13-, 15-, and 17-inch.
There have been two designs for the MacBook Pro, both using aluminum. The first design was largely a carry-over from the PowerBook G4 and used the Intel Core central processing units as opposed to the PowerPC G4 chips used in the model it replaced. It was first released as a 15-inch model in January 2006, followed by a 17-inch model in April of the same year. These original models received several updates and were upgraded with Core 2 Duo processors in late 2006.
The second “unibody” model has a more tapered design with most of the casing made from a single block of aluminum. This design was introduced with the 15-inch MacBook Pro in October 2008, along with the 13-inch aluminum unibody MacBook. The 17-inch model was updated with the same design the following January, also introducing the built-in battery that was later used in the rest of the MacBook Pro line from June and in the regular MacBook from October 2009. Apple updated the unibody line in April 2010 with Intel Core i5 and Core i7 processors in the 15- and 17-inch models, while the 13-inch models retained the Core 2 Duo processors. The most recent update, on February 24, 2011, added Thunderbolt ports to all three sizes. The 13-inch also received dual core i5/i7 processors and the 15-inch and 17-inch received quad core i7 processors.