What you type after the prompt is called a query. Queries should always end with a period and be followed by a carriage return. In fact, all of the grammar rules, definite clauses, macros and lexical entries in your programs should also end with periods. Most of the interface in ALE is handled directly by top-level Prolog queries. Many of these will return yes or no after they are called, the significance of which within ALE is explained on a query by query basis.