The application of 3rd party certification

iPhone OS is the operating system developed by Apple Inc. for the iPhone and iPod touch. Like Mac OS X, from which it was derived, it uses the Darwin foundation. iPhone OS has three abstraction layers: a Core Services layer, a Media layer, and a Cocoa Touch layer. The operating system takes less than half a gigabyte (GB) of the devices' total memory storage.At the 2007 Apple Worldwide Developers Conference Apple announced that the iPhone and iPod touch will support third-party "applications" via the Safari web browser, referred to as web applications. The applications can be created using web technologies such as AJAX. Many third party iPhone web applications are now available.

Currently, the iPhone and iPod touch cannot officially install full programs from anyone but Apple. However, many third party native applications are now available, despite this complete lack of support by Apple. Such native applications face the possibility of being broken by any iPhone OS update, though Apple has stated it will not design software updates specifically to break native applications (other than applications that perform SIM unlocking). These are available through the installer application, which is installed on the iPhone after major methods of jailbreaking. Some well known members of the 3rd party app community have switched over to the official SDK.

Since iPhone OS has been closed down the device from UMD (or UMPC), I can conclude that the Apple iPhone is not just a smartphone. It is a very high-end feature phone. As feature phones have increased functionality, input mechanisms, and outputs (displays and speakers), some feature phones have been very smartphone-like.