Emacs word wrap at a specific column number

Solution 1:

Type M-x auto-fill-mode to activate automatic line-wrapping after a certain column. Then set the actual line width through the variable fill-column as described by user choroba (C-x f).

Note though that this works a bit differently from what other text editors do. M-q will re-format the current paragraph.

Solution 2:

You can set the line width with C-xf (set-fill-column).

Afterwards, you might need to hit M-q to reformat the current paragraph (fill-paragraph), or select text to be justified and run fill-region.

Solution 3:

The suggestion for turn-on-auto-fill will work if you want hard newlines in the files you're editing. If not, and you just want word-wrap, consider instead visual-fill-column-mode, which just does the normal word-wrap that would happen at the edge of the window, but at the specified fill-column.

Solution 4:

See the Emacs manual (C-h r), node Filling. See in particular the first subnode in the menu, Auto Fill.