June 1, 2009

REXX - a Valuable Programming Tool on Titan

Titan customers who support Wylbur command procedures (CPs) will need to re-engineer their applications before Wylbur retires on December 31, 2009 (see the Titan News article Wylbur Will be Retiring). One option is to take advantage of the REXX programming language, available on Titan under TSO/ISPF.

What is REXX?

REXX (Restructured EXtended eXecutor) provides a fully functional application development environment, including structured programming techniques, logical and arithmetic operations, and communication with the TSO end user. This versatile programming language features a choice of compiled or interpretive execution, convenient built-in functions, free-format coding, debugging capabilities, and extensive parsing and character string manipulation. The REXX Compiler and Library allow users to translate frequently used routines into compiled REXX programs. The REXX Library also contains common routines that are accessible to all compiled REXX programs.

How is REXX accessed?

The Titan REXX compiler is available from TSO/ISPF interactively and in batch mode. After logging on to NIHTSO, you will see the CIT/Titan Primary Option Menu. On the Option line, type 4.14 for interactive access or 5.15 for batch access to the TSO/ISPF REXX compiler. You can create a program and save it as a z/OS Titan sequential data set or a partitioned data set (PDS). Remember: when using ISPF you must first allocate a data set before you can save it (check the Wylbur Retirement Wiki at http://wylretire.cit.nih.gov for tips on how to use ISPF).

Where is the REXX documentation?

REXX manuals are available from the CIT documentation service. Go to: http://publications.cit.nih.gov/category.asp?category=I004. This will bring you directly to the TSO section of the documentation service. Scroll down to see the REXX documentation. You can then view the manuals online and print them to your local printer (click on the monitor icon) or print the manual at the central data center printers (click on the printer icon). A Titan userid and password is required for central printing. The first copy of each manual printed on the central printers is available without charge to registered users.

Part 1 of the TSO/E REXX User's Guide provides a good introduction to REXX for inexperienced programmers who are somewhat familiar with TSO/E commands and have used ISPF. This manual has lots of examples and is intended both for beginner programmers and those with extensive programming experience. The TSO/E REXX Reference is useful for experienced programmers who have used a block-structured high-level language (e.g., PL/I, Pascal, or WYLBUR CPs). If you learned how to write Wylbur command procedures, you can learn how to use REXX.

Additional resources

PF1 Keys within ISPF

Take advantage of the extensive online help that is available from any ISPF panel, including the REXX panels. Once you have accessed the REXX panels within ISPF, just press the PF1 key for help related to the panel you are viewing.

Wylbur Retirement Wiki

Visit the Wylbur Retirement Wiki at http://wylretire.cit.nih.gov for tips on how to use ISPF and other tools available to Titan users to replace common Wylbur functions.

Help Desk

Contact the NIH Help Desk at http://ithelpdesk.nih.gov/support or 301-496-4357, 301-496-8294 (TTY), or toll free at 866-319-4357 with your questions and requests for assistance.

Interested in a class?

If you would like to attend a REXX class, please contact the NIH Help Desk. CIT will set up a class if sufficient interest is expressed by our users.