Which iPhone SDK should I use?

I have little knowledge about how to make application to compatible to a device.

I have iPhone SDK 4.0 and want my app to run on iOS 2.0 or later.

I have read that set only the iPhone OS Deployment Tar开发者_C百科get to 2.0 and use only those API methods which are common after 2.0.

Is it enough?

or do I have to use another (lower) SDK?

or do I have to do something more...?

You should always be developing with the latest SDK. You can set this in your project's properties under "Base SDK" in the "Architectures" section of your project's settings (right click on the project in the organizer, and go to "Get Info").

However, to make sure that your app runs on older devices, you would do this by setting the "iOS Deployment Target" to iOS 3.0 under the "Deployment" section of the project's settings.

For the record, I said version 3.0 above because that's the lowest possible supported version that I see in my Xcode. I don't think it's possible to target 2.0 devices anymore.

The newest Sdk. Apple may not accept the Sdk create by old Sdk.

You can target your min required version os for your App even you are using latest version Sdk.