From February 2015, the Cupertino-based company required all developers submitting applications to the App Store to include 64-bit support.
There are two ways to update your system, just make sure that your device has at least 50% battery and that you've cleared plenty of storage space—you'll need anywhere from 3 to 7GB free, depending on device.
See: The i OS 8 update can be installed on the i Phone 5S, i Phone 5C, i Phone 5, i Phone 4S, i Pad Air, i Pad mini Retina, i Pad mini, i Pad 4, i Pad 3, i Pad 2, and i Pod touch 5. Tap on the available update and hit Install—all you'll need is a strong Wi-Fi connection.
But, given Apple's previous history with server overloads and millions of people downloading the update at the same time, it's always more reliable to update via i Tunes.
If you have an i Phone 5 or an i Phone 5C, you will likely miss-out on the next major version of i OS.
That’s because Apple wants to move all i OS devices over to a 64-bit architecture, a plan that will more than likely coincide with the launch of i OS 11. Apple launched its first 64-bit i OS device back in September 2013, with the release of the i Phone 5S.