readme wip

README.md

@@ -40,8 +40,9 @@ Finally, additional assurance is maintaned since the integrity of resulting file
 </tbody>
 </table>
 
-| Option                     | Meaning |
-|----------------------------|---------|
+| Option                                                   | Meaning |
+|----------------------------------------------------------|---------|
+|`--backup, --restore, --check`|select mode of operation (only one at a time)|
 | `--buf-size <size_MB>` | buffer size to use when reading or writing (see _Memory usage_ section below for details) |
 | `--pass <password>` | password for encryption or decryption<br/>**WARNING:** it's impossible to restore the archive if password is lost! |
 | `--auth <auth_string>` | any arbitrary public authentication string that will be embedded into to archive; can be someone's name or passport ID, or company name; it's not kept in secret, but an attacker won't be able to impersonate this string |