Originally Posted by capoeira4u
Does this mean iPhone and iPad can now run the same "HD" apps? This will be great so I don't have to buy 2 copies of the same app, one for the iPhone and the HD version for the iPad.
Originally Posted by solipsism
A higher resolution display on the iPhone will not assist in using the "same" app. They still have very different size displays and aspect ratios. Think about it, elements designed for your finger on the iPad would be very tiny on the iPhone.
However, Apple did build their SDK to allow devs to build Universal apps that are one app that will work ideally on both the iPhone/Touch and iPad.
It's more than just display size and aspect ratio!
Some have said that: "the iPad is just a big iPod Touch." But it's not as, others have said: "that's like saying a swimming pool is just a big bathtub."
The additional real estate opens all kinds of possibilities.
-- in a bathtub your toys are pretty much limited to a rubber ducky, in the pool you can choose among inner tubes, lounge/drink carriers, water volley ball sets, slides, etc.
-- in the pool you can have lots of participants. doing various thiings... the tub is more limited to how many and what they can do
-- laps are a lot easier in the bathtub.
-- in the pool you can, likely, get away with wizzin' in the water... the bathtub, not so much.
Seriously, some apps can benefit from the additional real-estate:
-- games can have additional controls
-- drill-down apps can show several levels of data concurrently, instead of just 1
-- productivity apps can display (normally on) tool bars rather than popups
You really need to re-think an iphone app before porting it to an iPad (and soon, a 4G iPhone).
Fortunately, as Sol. points out, the iPhone SDK, has provisions for "Universal" apps: where the same core application code can exploit the different displays in a straight-forward and consistent way. This tends to isolate the differences in UI and navigation/application flow, while preserving the structure of the application.