After the system has been initialized, it will prompt the user for a query.
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It will continually accept user goals and solving for them
until the session is terminated with a halt/0 or if
it encounters the end of file (eg: 
D on UNIX or
Z on MSDOS).
This again is similar to the style of most PROLOG systems.
If the user goal failed then the ``*** No'' message is output, otherwise
the query is successful and the
resulting answer constraints (the constraints on variables in the
query) are output.
A successful query will also display a ``*** Yes'' message,
but if there are other alternatives to try for the query then
the ``*** Retry?'' message is displayed and the
user is prompted to either press carriage return or enter ``.'' (or ``n'')
to accept the
answers, or ``;'' (or ``y'') to cause backtracking.
A different prompt is displayed if delayed (nonlinear)
remain at the end
of the execution.
The message ``*** Maybe'' replaces ``*** Yes''
and ``*** (Maybe) Retry?'' replaces ``*** Retry?''
to indicate that the satisfiability of the nonlinear constraints remaining
has not been decided by CLP( 
).
Execution of a query can be interrupted at any time by using
the interrupt keycode ( C usually).
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A buffer of the last 50 goals is kept, and may
be examined by the history/0 (or h/0) predicate.
An old query may be re-executed by just
entering its history number as a goal (eg: ?- 5.).
For every top-level query. There is also an implicit dump on the variables in the goal, i.e. the set of answer constraints using those variables are printed, with the exception that anonymous variables and also other variables beginning with an ``_'' are ignored. No implicit dump is performed for goals embedded in a file. (Note that the output constraints differs from many PROLOG systems which display the variable bindings produced from execution.)