Setting window width in Xcode

Probably a very straightforward question. I'd like to set the width of the code editor in Xcode 4 to be exactly 80 characters. Where would I go to do that? Alternatively, if I can make a vertica开发者_运维知识库l line appear that indicates the 80 character, that would be fine as well.

Thanks.

In Xcode 4: Xcode menu -> Preferences -> Text Editing Tab -> check Page guide at column:.