The iPhone, like all smartphones and portable devices, is constantly being tweaked and updated by its creator, Apple. Every so often Apple will release new software for all of its iPhone models, and when you connect the device to iTunes or check the software update from the iPhone's menus you'll be prompted to download and install new software. This keeps your business phone running smoothly, although unplugging the USB cable while updating can lead to trouble.
Unplugging During Update
Though Apple doesn't specifically say what might happen if you were to unplug your iPhone during a software update, its official instructions for updating your iPhone specifically say "Do not disconnect your device until the update has finished." Like any software-based machine, the iPhone needs an operating system to function -- in this case iOS. If you were to shut your computer off halfway through an update or installation of Windows, the operating system might become corrupt and cease to work properly. Disconnecting the iPhone during an install could interrupt the flow of data and potentially corrupt the system files, leaving the phone inoperable, or "bricked."
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While Apple doesn't offer support for the consequences of unplugging your iPhone during a software update, a few iPhone users have reported that disconnecting the device during the update has lead to software issues such as the phone not turning on properly and not being able to access the Home screen upon booting the device. Most users experience an Apple or iTunes logo upon turning on the phone and then must troubleshoot their iPod to return it to factory settings.
Apple recommends always having the newest version of iTunes on your computer before doing an update. Additionally, the company suggests that you back up your iPhone before doing an update in the event that something goes wrong. To back up your iPhone, connect it to your computer, open iTunes, right-click on the device and choose "Backup." If you have an iCloud account, you can also back up to iCloud directly from your iPhone while on Wi-Fi or a data connection.
If, by chance, you happen to disconnect the cable to your phone during an update, don't panic. Plug the cable back in and let the iPhone continue to try to update. It's possible that a split-second disconnect won't be a problem and that iTunes will recognize the device instantly and continue the update. If you can't get the device to start working after accidentally unplugging it and can't get iTunes to recognize it to perform a factory reset, you may need to take it for professional service.