A storage class specifier is used to refine the declaration of
a variable, a function, and parameters. Storage classes determine
whether:
The object has internal, external, or no linkage
The object is to be stored in memory or in a register, if available
The object receives the default initial value of 0 or an indeterminate
default initial value
The object can be referenced throughout a program or only within
the function, block, or source file where the variable is defined
The storage duration for the object is maintained throughout program
run time or only during the execution of the block where the object
is defined
For a variable, its default storage duration, scope, and linkage
depend on where it is declared: whether inside or outside a block
statement or the body of a function. When these defaults are not satisfactory,
you can use a storage class specifier to explicitly set its storage
class. The storage class specifiers in
C and C++ are:
mutable
__thread