Fixes a bug with data transfer for some 3rd party accessories, including bar code scanners.
Launch i Tunes on your computer, select your i Phone on the list of devices and click the "Summary" tab.
Select "Check for Update" and then click "Download and Update" to initiate the update.
If i Tunes tells you that a more recent version of the application is available, download it.
Accept all prompts necessary to install the updated software.
This is the scenario facing owners of the i Phone 4. To help you make an informed decision, I've compiled the reasons in favor of and against upgrading an i Phone 4 to i OS 7 below.