Essentials of Subfile Programming and Advanced Topics in RPG IV [Paperback]

Phil Levinson (Author)

Book Description

Publication Date: November 1999

Many courses for AS/400 programmers stop short of teaching you subfile programming. Subfiles are the AS/400 tool that supports displaying lists of data on the screen, and in today's increasingly screen-based world, you must understand and be able to use them. In fact, every list that you have seen the AS/400 display has been created using the same programming techniques that you will learn in these chapters. This text introduces you to subfiles and leads you through the process of creating and debugging subfile programs. As new subfile concepts are presented, you will develop and expand the same programs to meet expanded specifications. This approach mirrors the real world in which new specifications continually add to the complexity of interactive programs. You will program interactive displays that help users find the data they need and update records as required. You will learn several techniques for designing screens that help make user displays intuitive and easy to use. In a later chapter, you'll learn to use two tools — journaling and commitment control — that will protect your database's integrity when programs let records be changed. The two ongoing sets of exercises in this text take you through the process of developing an inventory display screen and a purchase order line display screen with data maintenance capabilities. To get the most from this book, work through all segments of the continued exercises, as well as through the additional bookstore order system project that follows Chapters 5 and 7. Chapters 8 and 9 introduce Integrated Language Environment (ILE) tools for RPG. These include bound calls, multiple modules in a program, creating and using service programs, using procedures, and prototyping. Other advanced topics include using such file-oriented elements as record format level identifiers, the OVRDBF (Override with Database File) and OPNQRYF(Open Query File) CL commands, file and record locks, and file security; mining the file-information and program-status data structures for information; handling errors via the *PSSR subroutine, the INFSR keyword, and the Input/Output operation error indicator; and using data queues for program-to-program communication. Don't neglect the appendices! Appendix A explores the programming standards you'll meet in most IS departments and takes you beyond them into issues of programming style. Appendix B introduces debugging tools and techniques to support your programming skills. Finally, Appendix C gives you invaluable training in using Screen Design Aid (SDA). When you interview for a job as an AS/400 programmer, you will be asked about your knowledge of subfiles and other advanced RPG topics. Once you complete this text, its exercises, and the additional bookstore order system project, you'll have a head start on your first programming position or — if you're already a programmer — additional professional development that will count in your department and your company.

Editorial Reviews

From the Publisher

Today programs and systems are increasingly screen-based and interactive. Subfiles are the AS/400 tool that lets you display lists of data on the screen for user interaction. Your knowledge of subfiles is an important part of your professional development. Essentials of Subfile Programming and Advanced Topics in RPG IV teaches you to design and program subfiles, offering step-by-step instructions and real-world programming exercises that build from chapter to chapter. Chapters on the Integrated Language Environment (ILE), introduced concurrently with RPG IV, present tools and techniques that support effective modular programming. You’ll learn to design and create subfile records; load, clear, and display subfiles; develop display-file code and RPG IV code for interactive file maintenance; create pop-up windows for user interaction; and support users with advanced prompting features and Help screens. The book will further help you use Integrated Language Environmen! t (ILE) tools, including bound calls, service programs, procedures, and prototyping; link RPG IV programs and database files, using such features as the record format level identifier and the OVRDBF (Override with Database File) and OPNQRYF (Open Query File) commands; mine the rich store of information in the file-information and program-status data structures; handle errors using the *PSSR subroutine, the INFSR keyword and LO indicators, error messages, and error logs; improve data integrity with journaling and commitment control; and manage program-to-program communications, especially via the power of AS/400 data queues. Three useful appendices cover issues of programming standards and style, testing and debugging programs, and using Screen Design Aid (SDA).

About the Author

Philip J. Levinson brings more than 16 years of experience as an AS/400 programmer/analyst, consultant, and programming teacher at Jefferson College to presenting the essentials of AS/400 subfile programming. He holds a bachelor’s degree in Mechanical Engineering from the University of Hartford and a master’s degree in Management from Vanderbilt University. A member of the IBM-sponsored committee that developed the certification test for AS/400 programming, Phil lives in Olivette, Missouri, with his wife and twin sons.

Product Details

• Paperback: 293 pages
• Publisher: 29th Street Press; 293 edition (November 1999)
• Language: English
• ISBN-10: 158304051X
• ISBN-13: 978-1583040515
• Product Dimensions: 10 x 8.3 x 0.7 inches
• Shipping Weight: 1.3 pounds
• Average Customer Review: 5.0 out of 5 stars  See all reviews (2 customer reviews)
• Amazon Best Sellers Rank: #2,051,358 in Books (See Top 100 in Books)

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Customer Reviews

Most Helpful Customer Reviews

4 of 5 people found the following review helpful:

5.0 out of 5 stars Subfile Review, January 22, 2001

By 

Jill Zimmermann (St. Louis, MO USA) - See all my reviews

This review is from: Essentials of Subfile Programming and Advanced Topics in RPG IV (Paperback)

I used Phil Levinson's book after graduating with an As/400 degree. The subfile book is essential, and unique. It is the only on of it's kind to go into such detail about subfiles. The examples are easy to understand. The entire book and exercises takes you step by step so you can follow and learn. I would recomend this book to anyone who is new at using subfiles.

5.0 out of 5 stars Advanced Topics in RPG/400, June 16, 2011

By 

Acute Observer (N. Jersey Shore) - See all my reviews

This review is from: Essentials of Subfile Programming and Advanced Topics in RPG IV (Paperback)

Essentials of Subfile Programming, Phil Levinson

Philip J. Levinson has 15 years experience as an AS/400 programmer/analyst, consultant, and programming teacher at Jefferson College. He has a bachelor's degree in Mechanical Engineering and a master's degree in Management. This 260 page book has twelve chapters, three appendices, and an Index. Subfiles are the tool to support displaying lists of data on the screen. Journaling and commitment control will protect database integrity when records are changed. The application is for inventory control of a bookstore. Chapter 1 will show how to create subfile records and how to load, display, and clear a subfile. Chapter 2 shows how to delete and change records for interactive file maintenance. There are three methods for loading subfiles with multiple lists (Chapter 3). The next chapter shows how to display multiple lines per record.

Chapter 5 shows ways to locate records and load the desired data into the subfile. There are ways to make the system more user friendly and include the Help screens (Chapter 6). You can use subfiles in windows to provide advanced prompting features for users (Chapter 7). Chapter 8 has advanced concepts in linking RPG programs and database files. Chapter 9 shows the file-information and program-status data structures for normal processing and error handling. Error handling is explained in greater depth in Chapter 10. Chapter 11 explains journaling and commitment control to improve data integrity at the program and transaction levels. Data queues are explained in Chapter 12, they provide program-to-program communication.

An organization has standards for libraries and naming conventions (Appendix A). The author provides many practical suggestions for program arrangement and documentation. Appendix B offers good advice on testing and debugging programs. The best code is clean and easy to maintain. "Change is the only constant" said Heraclites. Appendix C explains how to use Screen Design Aid (SDA) to create, test, and edit displays.