Quick clarification on the iPhones released every year, and the corresponding OS:

2007: iPhone - iOS 1 (max iOS 3)
2008: iPhone 3G - iOS 2 (max iOS 4)
2009: iPhone 3GS - iOS 3 (max iOS 6)
2010: iPhone 4 - iOS 4 (max iOS 7)
2011: iPhone 4S - iOS 5 (max iOS 8)
2012: iPhone 5 - iOS 6 (upgradable to iOS 8)
2013: iPhone 5S and iPhone 5C - iOS 7 (upgradable to iOS 8)
2014: iPhone 6 and 6 Plus - iOS 8

Each year generally brings a faster device, and chops one off the support list for getting the latest OS release. Think of the hardware and iOS release as seperate, just as a computer could start with Windows XP and later be able to upgrade to Vista, 7, etc...

2013 did complicate things, the 5s was the faster phone (first 64 bit ARM smartphone out), while the 5C was just the 5 in a plastic shell. Apple keeps a few years worth of phones on the market to offer a variety of pricing options.

Apps in the app store can and often do have a minimum iOS version they need to run. And older phone is going to lose access to those updates sooner.

Originally Posted By: tfabris
Oh, and you can't tell by looking at the case whether it's a 4 or a 4s.

You can, as long as you are a member of the iFreak community wink (hint, it's all about the location of the antenna breaks).