Your iPhone's operating system (OS) tells you what functionality the device has and what software the device is compatible with. OS upgrades often optimize the device's performance by improving battery life and adding functionality to existing software, and adding new software and functionality. The most recent version of the iPhone OS is 4.3.1. You can locate what iPhone version is installed on your device using either the Settings app or iTunes.

Instructions

iPhone
1

Turn on the iPhone.
2

Tap the "Settings" app on the iPhone home screen.
3

Select "General."
4

Tap "About."
5

Scroll down to Version. The operating system version installed on your device appears to the right of Version.
ITunes
6

Open iTunes on your computer.
7

Connect your iPhone to the computer using the USB cable that came with the device.
8

Click the name of your iPhone after it appears beneath "Devices" on the left side of the iTunes program window.
9

Click the "Summary" tab on the right side of the program window. The operating system version installed on the phone is listed beneath iPhone and to the right of Software Version.