The firmware, or iOS software version, on your iPhone determines what apps your device supports, what bugs may not be addressed and what functionality you device has. For example, if your iPhone isn’t running at least iOS 3.0 firmware, your device won’t have copy and paste functionality. If your iPhone has a password lock that you can’t remember or just don’t want to bother entering, you can see what firmware the device is running by connecting your iPhone to your computer and opening iTunes.

How to Check Your Apple iPhone Firmware When It Has a Password Lock - 3