4.1.2 Terminology First, let’s look at the terminology used in this chapter. If you don’t get a thorough understanding of these terms, you will probably not understand much of what is said in the rest of this chapter. [Incident:] A situation, external or internal to the interpreter, which it is required to respond to in certain pre-defined manners. The interpreter recognizes incidents of several different types. The incident will often have a character of “suddenness”, and will also be independent of the normal control flow. [Event:] Data Structure describing one incident, used as a descriptor to the incident itself. [Condition:] Names the REXX concept that is equivalent to the incident. [Raise a Condition:] The action of transforming the information about an incident into an event. This is done after the interpreter senses the condition. Also includes deciding whether to ignore or produce an event. [Handle a Condition:] The act of executing some pre-defined actions as a response to the event generated when a condition was raised. [(Condition) Trap:] Data Structure containing information about how to handle a condition. [(Trap) State:] Part of the condition trap. [(Condition) Handler:] Part of the condition trap, which points to a piece of REXX code which is to be used to handle the condition. [(Trap) Method:] Part of the condition trap, which defined how the condition handler is to be invoked to handle the condition. [Trigger a Trap:] The action of invoking a condition handler by the method specified by the trap method, in order to handle a condition. [Trap a Condition:] Short of trigger a trap for a particular condition. [Current Trapped Condition:] The condition currently being handled. This is the same as the most recent trapped condition on this or higher procedure level. [(Pending) Event Queue:] Data Structure storing zero or more events in a specific order. There are only one event queue. The event queue contains events of all condition types, which have been raised, but not yet handled. [Default-Action:] The pre-defined default way of handling a condition, taken if the trap state for the condition raised is OFF. [Delay-Action:] The pre-defined default action taken when a condition is raised, and the trap state is DELAY.