Sometimes when you're editing a file with really long lines it's easier to work with the file if the lines don't wrap on screen. That's usually when I use the "no wrap" feature of the vi (or vim) editor.
If you don't want the lines to wrap in vi just type this command:
That command tells vi not to wrap the lines. The result is that any line that was wrapped before will now scroll off the screen to the right. If you want to return it to the default wrapping mode just type this command: