Switching views from portrait to landscape in iPhone just like the calculator in iPhone

I would like to know what is the best way to do what iPhone calculator does as far as switching view from portrait to landscape. To me it looks that the portrait UI is in a view that goes directly (with resizing) into a subview on the right sid开发者_开发问答e of the landscape view. And on the left side of the landscape subview there are more calculator buttons added. If this is a reasonable assumption of what is going on, I would like to know how to rotate the portrait xib file to become the right side of a subview in the landscape and furthermore add more stuff to the left side subview of landscape UI? Do I need a second xib file? Or do I rotate one xib file and add stuff in the code to the left subview?

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