While launching iPhone 5, Apple increased – vertically – the number of pixels available on the phone. This translated into an additional row of icons on the main screen and additional space for applications.
But, apps that were written for older versions of the iPhone, were displayed with bars at the top and the bottom of the application – quite like watching a cinemascope film that has black bars running at the top and the bottom of the screen – as the format is more wide in proportion.
With the release of the iPhone 6 and iPhone 6 Plus, this problem is going to be compounded. Now, application developers have to worry about apps that can be displayed correctly on a 3.5″ screen (iPhone 4), a 4″ screen (iPhone 5), a 4.7″ screen (iPhone 6) and a 5.5″ screen (iPhone 6 Plus).
With so many size configurations available, application developers will now have to worry a lot more about application layout when the app is executed on these form factors – making layout that much more difficult. This is the exact problem that faces Android developers, who have to worry about a wide variety of form factors, dimensions and DPI.