"Default arguments must be specified with the first occurrence of the
function name" means:

- If the function has a prototype above main and the function itself
  is defined below main, then the defult arguments must be specified in
  the prototype.

- If there is no prototype, but the function itself is defined above
  main, then the default arguments must be specified in the function
  header (and, in fact, there is nowhere else to define them).