Rexx provides queuing services entirely separate from interprocess communications queues.

The external data queue is a list of character strings that only line operations can access. It is external to Rexx programs in that other Rexx programs can have access to the queue.

The external data queue forms a Rexx-defined channel of communication between programs. Data in the queue is arbitrary; no characters have any special meaning or effect.

Apart from the explicit Rexx operations described here, no detectable change to the queue occurs while a Rexx program is running, except when control leaves the program and is manipulated by external means (such as when an external command or routine is called).

There are two kinds of queues in Rexx. Both kinds are accessed and processed by name.