Difference between Static variable declared in different scopes

Question

What is the difference between declaring static variable inside a block and outside a block in a file? Eg, here, what is difference between static variables a,b,c,d? Can we

Answer 1

Static variable inside a block(local static variable) -

1. It is not visible outside the block/function
2. It's value retains in function calls as it is static

Static variable outside a block(Global static variable) -

1. It's scope is the entire file(like a in your program)
2. It's value retains between function calls as it is static.