X'Terminated is an Ada attribute where X is any task object. This attribute indicates if X has terminated (true) or not (false).
Be warned -- calling X'Terminated can result in a race condition. X'Terminated may be false at the time the attribute value is read, but it may become true at the time action is taken based on the value read. Once X'Terminated is true, however, it can be expected to stay true.
See also 
- Ada Programming
- Ada Programming/Attributes
- Ada Programming/Tasking
- Ada Programming/Attributes/'Callable