Emacs has two different UIs: one using only a text console, the other using the window system. Even when a window system is present, Emacs can be started in a terminal emulator with the -nw option to show its text UI.

There are some customizations you might want to make conditional on the kind of UI. In my case, I use ECB, and in general I’d like it to start up automatically when I launch Emacs, but only when running in GUI mode.

It’s pretty simple to achieve this, a small addition to ~/.emacs does the trick.

(if (memq window-system '(x w32 mac))
  (ecb-activate))