Synopsis:
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.
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).
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