Globally-Defined Variables; Global Variables - Intel Extensible Firmware Interface Specification

17.2 Globally-Defined Variables

This section defines a set of variables that have architecturally defined meanings. In addition to the
defined data content, each such variable has an architecturally defined attribute that indicates when
the data variable may be accessed. The variables with an attribute of NV are non-volatile. This
means that their values are persistent across resets and power cycles. The value of any environment
variable that does not have this attribute will be lost when power is removed from the system and
the state of firmware reserved memory is not otherwise preserved. The variables with an attribute of
BS are only available before
environment variables can only be retrieved or modified in the pre-boot environment. They are not
visible to an operating system. Environment variables with an attribute of RT are available before
and after
ExitBootServices()
and modified in the pre-boot environment, and from an operating system. All architecturally
defined variables use the
#define EFI_GLOBAL_VARIABLE
{8BE4DF61-93CA-11d2-AA0D-00E098032B8C}
To prevent name collisions with possible future globally defined variables, other internal firmware
data variables that are not defined here must be saved with a unique
EFI_GLOBAL_VARIABLE. Table 17-1 lists the global variables.
Table 17-1 Global Variables
Variable Name
LangCodes
Lang
Timeout
ConIn
ConOut
ErrOut
ConInDev
ConOutDev
ErrOutDev
Boot####
BootOrder
BootNext
BootCurrent
Driver####
DriverOrder
Version 1.02
ExitBootServices()
is called. Environment variables of this type can be retrieved
EFI_GLOBAL_VARIABLE
\
Attribute Description
BS, RT The language codes that the firmware supports.
NV, BS, RT The language code that the system is configured for.
NV, BS, RT The firmware's boot managers timeout, in seconds,
before initiating the default boot selection.
NV, BS, RT The device path of the default input console.
NV, BS, RT The device path of the default output console.
NV, BS, RT The device path of the default error output device.
BS, RT The device path of all possible console input devices.
BS, RT The device path of all possible console output devices.
BS, RT The device path of all possible error output devices.
NV, BS, RT A boot load option. #### is a printed hex value. No 0x
or h is included in the hex value.
NV, BS, RT The ordered boot option load list.
NV, BS, RT The boot option for the next boot only.
BS, RT The boot option that was selected for the current boot.
NV, BS, RT A driver load option. #### is a printed hex value.
NV, BS, RT The ordered driver load option list.
12/12/00
is called. This means that these
VendorGuid:
VendorGuid
Boot Manager
other than
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