Man-machine communication comprises two types of information interchange, namely dialogue and output outside dialogue; they occur sequentially and in no particular order. Output outside dialogue is fully defined in Recommendation Z.316. Dialogue is that part of man-machine communication initiated and, normally, terminated by the user. It is accomplished by means of the dialogue procedures described in this Recommendation. In the text, the terms “dialogue” and “dialogue procedure” are used interchangeably. The text in § 2 describes the dialogue procedure, the syntax diagrams of which are given in § 3 in sub-divisions having numbers corresponding to those used in § 2. A systematic analysis of possible errors made by users is not considered. Diagrams mainly refer to correctly given commands and only obvious error situations are considered. It is recognized that the diagrams are not exhaustiveand some of them might be modified when error recovery procedures have been completely considered.