The Storage Class
1.Auto
The auto storage class is the default storage class for all local variables.
2.Extern
The extern storage class is used to give a reference of a global variable that is visible to all program files. When we use ‘extern’, the variable cannot be initialized as all it does is point the variable name at a storage location that has been previously defined.
3.Static
The static storage class instructs the compiler to keep a local variable in existence during the life-time of the program instead of creating and destroying it each time it comes into and goes out of scope.
4.Register
The register storage class is used to define local variables that should be stored in a register instead of RAM. This means that the variable has a maximum size equal to the register size and can’t have the unary ’&’ operator applied to it.