OS X
All the power and sophistication of the world’s most advanced operating system — OS X — is now available on a small, handheld device that gives you access to true desktop-class applications and software, including rich HTML email, full-featured web browsing, and applications such as widgets, Safari, calendar, text messaging, Notes, and Address Book. iPhone is fully multi-tasking, so you can read a web page while downloading your email in the background. This software completely redefines what you can do with a mobile phone.