OS X

Apple has confirmed that an optimized version of the Mac OS X operating system (without unnecessary components) runs on the iPhone, although differences between the operating system (OS X) running on Macs and the iPhone have not been officially explained. As iPhone's CPU is an ARM processor, the version of OS X that runs on iPhone differs from the desktop version in that it is written for the ARM instruction set architecture (ISA) instead of the x86 and PowerPC ISAs that the Mac version of OS X is written for.
The operating system takes up about 700 MB of the device's total 4 or 8 GB storage.[9] It will be capable of supporting bundled and future applications from Apple.
Apple intends to offer a smooth method for updating the iPhone's operating system, in a similar fashion to the way that Mac OS X and iPods are updated, and touts this as an advantage compared to other cell phones.[19]
Widgets, similar to the ones available in Mac OS X v10.4's Dashboard, are included on the iPhone. They include Stocks and Weather widgets.
The iPhone's version of OS X includes the software component "Core Animation" which is responsible for the smooth animations used in its user interface. Core Animation has not yet been released for Macs, but will be part of Mac OS X v10.5.
The build of OS X on at least one iPhone is "OS X 1.0 (1A543a)", as seen in a crash log for the MobileMail application.[20][21] The application apparently runs as the superuser.