Multitasking (iOS)
Multitasking was first released in June 2010 with the release of iOS 4.0.  Only iPhone 4, iPhone 3GS, and iPod Touch 3rd generation were able to use multitasking. The iPad did not get multitasking until iOS 4.2 was released in November 2010. Multitasking is currently supported on iPhone 3GS or newer, iPod Touch 3rd generation or newer, and all iPad models.