Base-SDK of v4.0 means it won't install on 4.1 or 4.2 devices?

I was using xCode v3.2.3 and SDK 4.0 to write iPhone apps that worked on my iOS v3.1.3 device... as well as v4.0. (Deployment target set to 3.1.3. Base SDK set to v4.0)

Does that mean everyone that uses my app will need a minimum of iOS 3.1.3 and a maximum of v4.0? Or will they also run on v4.1 and v4.2?

Second part of my question:

I now upgrade my iOS v3.1.3 to v4.2.1.

Xcode now says my v4.2.1 device is now no longer provisioned.

Doesn't a Base-SDK setting of v4.0 mean apps will also run (or at least install) on v4.x?

No. Base SDK just means that your app will be built against the iOS 4.0 libraries. Any 4.x device will be able to run a release build of your app, but for debugging, Base SDK and the iOS version on your device must match. In the end, you need to build your app with the newest available Base SDK anyway, because Apple won't accept apps built for older SDKs into the App Store.

No, they will. iOS has Backward compatibility.

I agree with Irene. I found the solution:

• The hint came from here: Can't make Xcode 4 run a barely empty project using SDK 4.2 (runs fine in 4.3)

• And this is how i resolve: my xcode 4.0 my SDK 4.3 and my Ipod touch device is 4.2.1 - You see it is backward compatible. There are 2 things you must do in order to resolve. 1) In your xcode 4.0, You click on your project name under Target to ensure you change the target not the Project setting. Find the row >IOS deployment target to the version of your device in my case it was back to 4.2.1 ipodtouch so i set 4.2 (do not worry about basesdk it is for your application not the same as your application's target. 4.3 basesdk requires you provide codesign so you have to select code sign if do not have one apply for one looking up in Apple website or google)

• After setting your target to compatible version with your device you now can go to "set the active scheme" that is where you select which device to install and run on including the simulator. So you will find you device there select it and you are good to go.

And if you still can not get it going. You can try to select your project under Project this time adn set the ios deployment target to your version mine was 4.2 ipodtouch ios. Then go select "set the active scheme" that is where you select which device to install and run on including the simulator. So you will find you device there select it and you are good to go.