How to create Universal app for iOS?

I need to create universal app for iPhone 3.5, 4.0, 4.7, 5.5 inches mobile and iPad. Also i wish to know which is the best way whether to create programatically or to use storyboard. I am using xcode-6.

Solution

When creating a new project, you need to specify for which device you want to build the app, having the options iPhone, iPad and Universal. So, in your case you need to specify Universal.

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As for the question whether or not to use Storyboards, it depends a bit on your app. But especially when you want to go for all devices and device sizes, I guess it's a good idea to use Storyboards and then also make use of Autolayout and Size classes to adapt your UI to the different screen sizes.