The iPhone is running an optimised but full version of OS X that weighs in at “considerably less” than half a GB, according to Apple vice president of worldwide iPod marketing Greg Joswiak.

Joswiak confirmed that the operating system sits in the flash memory of the device and that Apple will “provide updates to the operating system like we do today.”

He emphasised: “Apple has a proven and very smooth update mechanism for everything from our computers to our iPods. We will follow that kind of model here, which is an advantage a lot of phones don’t have.”

Joswiak claimed that the reduced size of the operating system was a result of expertise of the team at Apple, rather than cutting out functionality or removing core technologies. “Remember that OS X on a Mac features a lot of applications that we don’t have to ship on the iPhone,” he added.

The optimised operating system sits in the flash memory. According to Joswiak, Apple chose flash because it is “more versatile” than a hard drive, this decision ruled out a larger hard drive, at least for now. “Flash has some nice advantages for us in putting it in that form factor. It’s very small and very durable,” Joswiak said.

This is one in a series of five articles featuring comment from Apple about the iPhone. Read more here:

Macworld Expo: The iPhone 'price is right'

Macworld Expo: Optimised OS X sits on 'versatile' flash

Macworld Expo: No 3rd party iPhone software

Macworld Expo: Everyone wants a piece of the iPhone

Macworld Expo: 3G future for iPhone