Tips for updating to iOS 11The new operating system features a customisable Control Centre. The bad news is that some older, but still popular, devices will not be able to update to iOS 11. iOS 11 will only work on newer iPhones that have a 64-bit processor which allows the system to use larger amounts of memory. Older iPhones have a 32-bit processor. If apps are optimised for 32-bit devices then they won't work on iPhones after the iOS 11 update.

Source: Stuff September 19, 2017 00:45 UTC