为什么一部影片中会出现director和directed by

一样. 都是谁谁谁导演的 不可能一部戏这两个写法一起出现的吧...
ps. 编剧是screenwriter或是screenplay by 谁谁谁

好像Director, Directed by, A Film by 指的都是导演吧。

director不是导演，而是编剧，directed by是由...导演之意．

director 导演
directed by 由...导演