3.9.3 Environment variables
Device paths are also used when certain environment variables are built and stored in non-volatile storage. There are a number of environment variables defined in the Boot Manager chapter of the UEFI Specification. These variables define the following:
Console input devices
Console output devices
Standard error devices
The drivers that need to be loaded prior to an OS boot
The boot selections that the platform supports
The UEFI boot manager, UEFI utilities, and UEFI-conformant operating systems manage these environment variables as operating systems are installed and removed from a platform.