In this task, the job is to create a new empty file called "output.txt" of size 0 bytes
and an empty directory called "docs". This should be done twice: once "here", i.e. in the current working directory and once in the filesystem root.

# let oc = open_out "output.txt" in
  close_out oc;;
- : unit = ()
 
# Unix.mkdir "docs" 0o750 ;; (* rights 0o750 for rwxr-x--- *)
- : unit = ()