The final delimiter of an interactive stream:

This final delimiter is never actually seen by programs; no need to test for #\^D or #\^Z - use READ-CHAR-NO-HANG to check for end-of-stream. Calling CLEAR-INPUT on the stream removes the end-of-stream state, thus making it available for further input.

A newline character can be entered by the user by pressing the Newline key or, on the numeric keypad, the Enter key.