1.2. Differences Between iPhone and iPad

The most striking, and obvious, difference between the iPhone and the iPad is screen size. The original iPhone screen has 480×320 pixel resolution at 163 pixels per inch. The iPhone 4 and 4th generation iPod touch Retina Displays have a resolution of 960×640 pixel at 326 pixels per inch. Meanwhile both generations of the iPad screen have 1024×768 pixel resolution at 132 pixels per inch. This difference will be the single most fundamental thing to affect the way you design your user interface on the two platforms. Attempting to treat the iPad as simply a rather oversized iPod touch or iPhone will lead to badly designed applications. The metaphors you use on the two different platforms

The increased screen size of the device means that you can develop desktop-sized applications, not just phone-sized applications, for the iPad platform. Although in doing so, a rethink of the user interface to adapt to multi-touch is needed. What works for the iPhone or the desktop, won’t automatically work on an iPad. For example, Apple totally redesigned the user interface of the iWork suite when they moved it to the iPad. If you’re intending to port a Mac OS X desktop application to the iPad you should do something similar.