Hardcore vi memory aid, bare

From Clubnix.net

WRITING TEXT (MEMORY AID ITSELF)
                   or more        O
     i.a          correctly       I   i.a     A
      o                           o


SCRATCHING TEXT (MEMORY AID ITSELF)
     d?

     ^     X.x     $
            DDDDDDDD


SCRATCHING+WRITING TEXT (MEMORY AID ITSELF)
           replace by same char r   R keep replacing
        substitute by insertion s   S substitute lines
     change object by insertion c?  C change till end of line