I am begging you to not turn IOS into the next Internet Explorer. That would be so sad. Granted, the backwards compatibility is ‘ok’, but it’s not amazing. For starters, storyboards don’t really work on IOS4. Xcode 4.3 does not include a fully working set of command line tools by default. Nothing will build without it, despite the fact that xcode-select and which make may return correct values.
You must open Xcode, go to Preferences, and download this component from the Downloads section. You will require an Apple ID to download the component.
This Case study talks about how a iphone developer can integrate AdMob SDK into native xCode project, this is a very basic case study and very useful for some one who is integrating AdMob SDK for first time.