How do I get Aquamacs/Emacs to show a right margin indicator?

After living with Java IDE's for quite some time now, I'm back into the worl开发者_JS百科d of C++ development. And I've returned to my editor of choice: Emacs (actually, most of the time I'm in Aquamacs on the Mac, but I do occasionally use Emacs when I'm on a Linux box).

Strangely, the thing I find myself missing most is a right margin indicator. I find myself using M-x 3 a lot to put code up side by side. Knowing exactly where I've set the margin would help me keep things clean and neat.

Is there any hope of setting up Aquamacs to show a right margin indicator? Or something that would have a similar effect? How about Emacs with X support?

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You can use the column-marker library to set column markers with specific faces.

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using C-u 80 # I can quickly insert # 80 times to separate chunks of code.

this also acts as visual guide so I don't go above 80 characters on single line, a common coding convention (perhaps same as your reason)

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C-u followed by a number and then a command, repeats the command the given number of times

eg, C-u 10 C-n will move cursor 10 lines down