static

It's all about scope, duration and linkage!

outside of a block

• It defines a global variable with internal linkage, meaning the variable could only be used in the file in which it was defined.

inside a block

• Using the static keyword on local variables changes them from automatic duration to static duration.
• A static variable retains its value even after the scope in which it has been created has been exited!
• Static duration variables are only created (and initialized) once, and then they are persisted throughout the life of the program.

inside a class

variable

• shared by all objects of the class
• exist even if no objects of the class have been instantiated
• belong to the class itself, not to the objects of the class

function

• not attached to any particular object
• can be called directly by using the class name and the scope resolution operator
• have no this pointer! (the this pointer always points to the object that the member function is working on)
• can only access static member variables.