5.13.5 Other Parts of the I/O System
This section lists some of the other parts of REXX and the
environments around REXX that may be considered a part of the I/O
system.

[Stack.]
     The stack be used to communicate with external environments.
     At the REXX side, the interface to the stack is the
     instructions PUSH, PULL, PARSE PULL, and QUEUE; and the built-
     in function QUEUED().  These can be used to communicate with
     external programs by storing data to be transferred on the
     stack.

[The STREAM() built-in function.]
     This function is used to control various aspects about the
     files manipulated with the other standard I/O functions. The
     standard says very little about this function, and leaves it
     up to the implementor to specify the rest. Operations like
     opening, closing, truncating, and changing modes

[The SAY instruction.]
     The SAY instruction can be used to write data to the default
     output stream. If you use redirection, you can indirectly use
     it to write data to a file.

[The ADDRESS instruction.]
     The ADDRESS instruction and commands can be used to operate
     on files, depending on the power of your host environments
     and operating system.

[The VALUE() built-in function.]
     The function VALUE(), when used with three parameters, can be
     used to communicate with external host environments and the
     operating system. However, this depends on the implementation
     of your interpreter.

[SAA API.]
     The SAA API provides several operations that can be used to
     communicate between processes. In general, SAA API allows you
     to perform the operations listed above from a binary program
     written in a language other than REXX.

And of course, I/O is performed whenever a REXX program or
external function is started.


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