Make universal binary for IOS4 (iPhone 4) and 3G

How to make universal binary of one app, which can correctly run on 3G and support multitasking on iP开发者_开发问答hone 4? Thanks!

The term "universal binary" here is a misnomer, since that is only for iPad/iPhone combined apps. If all you want to do is compile a build that works on both iPhone 4 and iPhone 3G, you need to download and install SDK 4, set 4.0 as the "Base SDK", and then set your "Deployment Target" to whatever minimum version of iOS you want to allow to run your app. Some people use a setting of 3.1.3, some people keep that setting at 4.0.

This is documented in the iPad Programming Guide under Starting Your Project.