iPhones run on an operating system, and each time a new iPhone is released, the OS is upgraded and the number is changed. It's important to know which iPhone you have to learn more about available features. It's also important to know what iPhone you have if you need to contact customer service, or if you are looking for accessories or replacement parts. The OS number can be found on your iPhone, or through iTunes by hooking up to your computer.
Tap the "Settings" icon from the Home screen on your iPhone.
Scroll down and tap "General" in the third group of settings options.
Tap "About" at the top of the screen.
Scroll down to "Version." The number listed to the right of "Version" is the OS your phone is running on.
Plug your iPhone into your computer using the Dock Connector to USB Cable. iTunes should automatically open up on your computer. If it doesn't, click it to open.
Select your iPhone device on the left side of the computer screen if it doesn't automatically open.
Click on the "Summary" tab. It will display a photo of your phone, along with other information. The OS number for your iPhone will be listed near the centre of the screen under the heading "Software Version."