declares an automatic variable
Management type and size variables are automatic, no statement is, in principle, necessary.
Their visibility and permanence can be:
Automatic (no statement)
It is known that within the function where it is defined (without declaration), and it is lost output.
It is known that within the function where it is defined and retains its value.
It is known wherever it is so declared.
It is known in all program functions defined on an object and unknown to the outside.