Please note, this blog entry is from a previous course. You might want to check out the current one.
The third assignment is yet a further extension of the calculator built in the previous assignments.
When your application is run on the iPhone, it must present the user-interface of your calculator from Assignment 2 inside a UINavigationController.
Just go to your storyboard, select the existing CalculatorViewController and embed it into a new UINavigationController clicking Editor -> Embed in -> Navigation Controller. Then double click the newly created navigation bar inside the CalculatorViewController and name it “Calculator”.