Emacs: check for no-window-system in .emacs

Question

is it possible, to check if emacs is running in --no-window-system (-nw) mode within the dot-emacs file (.emacs)? I would like to enable/include certain extension only if emacs is in window mode (/or not).

Kind regards, mefiX

Answer 1

The variable window-system is nil if the selected frame is on a text-only terminal.