nl

Enable the underlying display device to translate the return key into newline on input, and whether it translates newline into return and line-feed on output (in either case, the call ::addch('n') does the equivalent of return and line feed on the virtual screen).

Initially, these translations do occur. If you disable them using ::nonl, curses will be able to make better use of the line-feed capability, resulting in faster cursor motion. Also, curses will then be able to detect the return key.