How to support different iOS versions?

I just uploaded a beta of my app to http://testflightapp.com. I noticed that it is only for iOS 4.3.

How can I support devices from iOS 4.0? Do I have to make the ipa for each framework version?

Any 开发者_JAVA技巧suggestions?

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Set the iOS Deployment Target in your build settings to the oldest version you want to support.

Please note that this doesn't automatically make sure that your code actually works on the older API (for example if you use stuff in the frameworks that's only available in the latest version ... )