Siri is an intelligent software assistant and knowledge navigator functioning as a personal assistant application for iOS. The application uses a natural language user interface to answer questions, make recommendations, and perform actions by delegating requests to a set of web services. Siri claims that the software adapts to the user's individual preferences over time and personalizes results, as well as accomplishing tasks such as making dinner reservations and reserving a cab.
Siri was originally introduced as an iOS application available in the App Store. Siri was acquired by Apple Inc. on April 28, 2010. Siri had announced that their software would be available for BlackBerry and for Android-powered phones, but all development efforts for non-Apple platforms were cancelled after Apple's purchase.
Siri is now an integrated part of iOS 5, and available only on the iPhone 4S, launched on October 4th 2011, the day before Steve Jobs died. Despite this, hackers were able to adapt Siri in previous iPhones. On November 8, 2011, Apple publicly announced that it had no plans to support Siri on any of its older devices.
Independent developers claim that they ported Siri to iPhone 4. However, some news sites consider that the videos they posted for proof only show the user interface of the application, excluding any voice commands, to conclude that they did not prove anything. However, new sources suggests that the independent developers are able to port Siri to the iPhone 4, iPod Touch, and iPad.