Simply unplugging an iPhone from your computer is never a good idea. Like any other USB device capable of interacting with your computer, it may be in the process of updating files when you pull it from the computer. This could corrupt data on the iPhone or your computer and could make your iPhone inoperable. Ejecting the iPhone ensures that any processes between the iPhone and your computer are stopped before you pull the plug.
Ejecting in iTunes
Look at the status bar at the top of the iTunes window. Wait for any process to finish or click the "X" beside the status to stop the current process.
Click the "Eject" button beside the iPhone in the list of devices. Wait for the iPhone's name to disappear.
Safely disconnect the iPhone from the computer's USB port.
Ejecting an iPhone in Windows
Move the cursor to the upper right corner of the Windows 8 desktop and then drag it downward to reveal the desktop sidebar. If you have a touch screen, drag your finger to the right edge of the desktop. Select "Settings" and then "Change PC Settings."
Select "Devices" and then select your iPhone from the list of devices. Click or tap the iPhone's "Remove" icon and then select "Remove."
Safely unplug the iPhone from the computer.
Information in this article applies to iTunes 11, Windows 8 and Mac OS X 10.8 Mountain Lion. It may vary slightly or significantly with other versions or products.