Device Firmware Upgrade (DFU) mode

A mode in which a device’s Boot ROM code waits to be recovered over USB. The screen is black when in DFU mode, but upon connecting to a computer running iTunes or the Finder, the following prompt is presented: “Finder (or the iTunes) has detected an (iPhone or iPad) in Recovery mode. The user must restore this (iPhone or iPad) before it can be used with Finder (or the iTunes).”