IOS: change firmware

I installed Xcode 4 with IOS 4.3 and I create an small application, but if I want set firmware 4.2? How can I do? 开发者_运维知识库In build menu I can choose only 4.3 for IOS.

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Always set Base SDK to the Latest iOS. This will ensure compatibility with current and future versions.

To make your app run on older versions of the OS, set the Deployment Target to the desired version in your Active Target's settings.