The MacBook Pro is a line of Macintosh portable computers by Apple Inc. First introduced in January 2006 at the Macworld Expo alongside the Intel-based iMac, the MacBook Pro replaced the PowerBook G4 and was the second computer to be announced in the Apple Intel transition (after the iMac). Positioned at the high end of the MacBook family, the MacBook Pro is aimed at the professional and power user market. There have been two designs for the MacBook Pro, both using aluminum. The first design was largely a carry-over from the PowerBook G4. The second "unibody" design is a more tapered design with most of the casing made from a single block of aluminum.