until — Continue to execute the body as long as the condition is not true.
until( : : Condition : )
until ends a
until loop is executed as long as the
Condition parameter evaluates to 'false' (0).
The body of the loop is executed at least once, because the condition
will be checked at the end of the body.
Condition for loop.
If the values of the specified parameters are correct,
until (as operator) returns TRUE. Otherwise, an
exception is raised and an error code returned.