Input/Output

PL/I has very rich I/O capabilities. Record I/O is the most efficient, and STREAM I/O is the least efficient. If you must use STREAM I/O, LIST-directed is the best form to use, followed by EDIT-directed, and lastly DATA-directed.

It is a good practice to:

• Declare files with all attributes.
• Explicitly OPEN a file when needed, and CLOSE when done.
• Establish ON units to handle I/O conditions.
• Use 'move mode' (that is, READ FILE(x) INTO(s)) for record I/O, as it is the most efficient method.

DISPLAY [REPLY] is generally not suitable for production programs, and should be restricted to use only as a 'quick and dirty' debug aid.

See Enterprise Server Considerations to determine if I/O is suitable in mainframe subsystem environments.