IPSW files are essentially just packages to deliver updates to your i Phone, i Pad, and i Pod touch including the baseband and firmware.
Note: It is possible that a friend might see an alert for the update before you do!
As you can see from the steps above, it's very easy to update the i Phone or i Pad operating system, but before you do so we recommend that you take some steps to protect your data before you click yes on that update alert.
For that reason we recommend backing up to your computer as well as i Cloud.
As a general principle this is a sensible idea - you may change your mind and decide you want to downgrade from i OS 11 to i OS 10, and this will be easier if you make sure you've got a copy of the latest version of i OS 10 compatible with your device.
Beware though that at some point Apple will stop "signing" older versions of i OS so it will become impossible to downgrade.
If you have a copy on your hard drive you will find it by following this path: Library/i Tunes and then select the Software Updates folder for your device.Any i Phone IPSW files that you have already downloaded from i Tunes are stored locally on your machine.You can access these directly at the following locations: Mac OS X: ~/Library/i Tunes/i Phone Software Updates Windows XP: \Documents and Settings\username\Application Data\Apple Computer\i Tunes\i Phone Software Updates Windows Vista & Windows 7: \Users\username\App Data\Roaming\Apple Computer\i Tunes\i Phone Software Updates The IPSW acronym is thought to stand for i Phone Software.Beware: the backup will include purchased music, TV shows, apps, and books; photos and video in the Camera Roll; and device settings, but it won't include anything you synced from your computer.To re-sync that stuff you'll need to sync with i Tunes.Use that information to download the appropriate IPSW for the device.