Define External Static Storage Class - Computer Programming?

An external static is declared outside of all the functions and is obtainable to all functions in that program. The difference between a simple external variable and a static external variable is that the static external variable is available only within the file where it is defined while the simple external variable can be accessed by other files.

It is as well probable to control the scope of function by declaring as static by giving a function in the file in that it is defined and not to any function in other files.