4.2.1 Information Regarding Conditions (data structures) There are mainly five conceptual data structures involved in conditions. [Event queue.] There is one interpreter-wide queue of pending conditions. Raising a condition is identical to adding information about the condition to this queue (FIFO). The order of the queue is the same order in which the conditions are to be handled. Every entry in the queue of pending conditions contains some information about the event: the line number of the REXX script when the condition was raised, a descriptive text and the condition type. [Default-Action.] To each, there exists information about the default-action to take if this condition is raised but the trap is in state OFF. This is called the “default-action”. The standard default-action is to ignore the condition, while some conditions may abort the execution. [Delay-Action.] Each condition will also have delay-action, which tells what to do if the condition is raised when condition trap is in state DELAY. The standard delay-action is to queue the condition in the queue of pending conditions, while some conditions may ignore it. [Condition traps.] For each condition there is a trap which contains three pieces of status information: the state; the handler; and the method. The state can be ON, OFF or DELAY. The handler names the REXX label in the start of the REXX code to handle the event. The method can be either SIGNAL or CALL, and denotes the method in which the condition is to be handled. If the state is OFF, then neither handler nor method is defined. [Current Trapped Condition.] This is the most recently handled condition, and is set whenever a trap is triggered. It contains information about method, which condition, and a context-dependent description. In fact, the information in the current trapped condition is the same information that was originally put into the pending event queue. Note that the event queue is a data structure connected to the interpreter itself. You operate on the same event queue, independent of subroutines, even external ones. On the other hand, the condition traps and the current trapped condition are data structures connected to each single routine. When a new routine is called, it will get its own condition traps and a current trapped condition. For internal routines, the initial values will be the same values as those of the caller. For external routines, the values are the defaults. The initial value for the event queue is to be empty. The default- action and the delay-action are static information, and will always retain their values during execution. The initial values for the condition traps are that they are all in state OFF. The initial value for the current trapped condition is that all information is set to the nullstring to signalize that no condition is currently being trapped.