static Local Variables

When you apply the static modifier to a local variable, the compiler creates permanent storage for it,
much as it creates storage for a global variable. The key difference between a static local variable
and a global variable is that the static local variable remains known only to the block in which it is
declared. In simple terms, a static local variable is a local variable that retains its value between
function calls.
static local variables are very important to the creation of stand-alone functions because several
types of routines must preserve a value between calls. If static variables were not allowed, globals
would have to be used, opening the door to possible side effects.