Intel Extensible Firmware Interface, Specification

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Services
Version 1.02 12/12/00 77
3.5 Variable Services
Variables are defined as key/value pairs that consist of identifying information plus attributes (the
key) and arbitrary data (the value). Variables are intended for use as a means to store data that is
passed between the EFI environment implemented in the platform and EFI OS loaders and other
applications that run in the EFI environment.
Although the implementation of variable storage is not defined in this specification, variables must
be persistent in most cases. This implies that the EFI implementation on a platform must arrange it
so that variables passed in for storage are retained and available for use each time the system boots,
at least until they are explicitly deleted or overwritten. Provision of this type of non-volatile
storage may be very limited on some platforms, so variables should be used sparingly in cases
where other means of communicating information cannot be used.
Table 3-10 lists the variable services functions described in this section:
Table 3-10. Variable Services Functions
Name Type Description
GetVariable Runtime Returns the value of a variable.
GetNextVariableName Runtime Enumerates the current variable names.
SetVariable Runtime Sets the value of a variable.