Use Automatic Reference Counting no longer need to manually release the memory it?

When you create a new project in Xcode 4, increasing the Use Automatic Reference Counting option is not possible without having to manually release the memory of?

What is the minimum version of the IOS supports ARC is?
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IOS5.0 began to support ARC. ARC is a compile-time technique using ARC function, programmers do not need to use the release code, autorelease up, Xcode will automatically add you at compile time. If you add, it will fail to compile.
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ARC in the actual project what the advantages and disadvantages?
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Only drawback! The advantage is less knock a few lines of code.
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ios4.0 will support arc, the advantage is that the compiler will help retain and release you write code, you do not have to worry about this anymore yourself completely. But this does not mean that the object is not released, but the compiler to help you write code release, when the release will be released
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Do not mislead others, 1st Floor, ios4 fully support arc, I have a project with a debug arc, debug the system without pressure to ios4.3
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references, 5th Floor reply:

1 floor, do not mislead people, ios4 fully supported arc, I have a project debug with the arc, debug to ios4.3 The system has no pressure

Might say a bit ambiguous, ARC is a compile-time technique is the concept Apple when Xcode4.2, IOS5 release raised, Xcode4.1 not supported, but support IOS4 and IOS5. So there is an official statement: ARC is supported in Xcode 4.2 for Mac OS X v10.6 and v10.7 (64-bit applications) and for iOS 4 and iOS 5 Weak references are not supported in Mac OS X v10.6 and. iOS 4.