Specifying Numeric Arguments
----------------------------

`digit-argument (M-0, M-1, ... M--)'
     Add this digit to the argument already accumulating, or start a new
     argument.  <M-> starts a negative argument.

`universal-argument ()'
     Each time this is executed, the argument count is multiplied by
     four.  The argument count is initially one, so executing this
     function the first time makes the argument count four.  By
     default, this is not bound to a key.