There are 3 main uses for the static.
1. If you declare within a function:
It retains the value between function calls
2.If it is declared for a function name:
By default function is extern so it will be visible from other files, if the
function declaration is as static it is invisible for the outer files
3. Static for global variables:
By default we can use the global variables from outside files If it is
static global that variable is limited to with in the file