defaulting and completion in the standard manner (@pxref{File Names}).
While in the minibuffer, you can abort @kbd{C-x C-f} by typing @kbd{C-g}.
+@cindex file selection dialog
+ When Emacs is built with a suitable GUI toolkit, it pops up the
+standard File Selection dialog of that toolkit instead of prompting for
+the file name in the minibuffer. On Unix and GNU/Linux platforms, Emacs
+does that when built with LessTif and Motif toolkits; on MS-Windows, the
+GUI version does that by default.
+
Your confirmation that @kbd{C-x C-f} has completed successfully is the
appearance of new text on the screen and a new buffer name in the mode
line. If the specified file does not exist and could not be created, or