Kelton Carson

Although this review is being written in 2008, some 34 years after the book itself was written, it still has relevance because of RPG's survival into the 21st century.

This book is divided into two parts. Part One is devoted to computer fundamentals. The hardware described and illustrated includes the IBM 029 keypunch machine, the IBM 2501 card reader, the IBM 2741 keyboard terminal, the IBM 1403N-1 high-speed line printer, and the IBM 1442M card punch. Carson also tells about paper-tape punch machines, magnetic tape systems, and graphic display devices.

Carson reduces the fundamentals needed for RPG programming down to seven computer functions: (1) Addition, (2) Subtraction, (3) Division, (4) Multiplication, (5) Equal To, (6) Greater Than, and (7) Less Than.

Carson concludes Part One with a chapter on standard 80-column punch cards.

Part Two is devoted to RPG programming. In the chapter on RPG basics, Carson assures his readers that RPG can do everything COBOL can do, and do it faster and easier.

RPG is easy to learn because programming is done on four preprinted forms: (1) the file description form, (2) the input specification form, (3) the calculation specification form, and (4) the output format specification form.

The Hardest Chapter. The biggest and hardest chapter in the book is Chapter Nine, "RPG Problem Workbench." By means of a series of eight problems, sequenced from simple to complex, Carson shows his readers how to analyze a problem, draw a flow chart, organize a sample printout, and write the program onto blank RPG forms. After solving these eight problems and writing the related programs, readers will find themselves well along the path that leads to mastery of RPG programming.

Missing Chapter. Mr. Carson made a promise in the Preface and again in Chapter Four that Chapter Eleven would provide some valuable reference material. Furthermore, the information provided would be presented "in a more concise and correlated form than the form in which it is found in manufacturers' handbooks." Alas, there is no Chapter Eleven in this book. Instead, the book concludes with Chapter Ten, a chapter on program diagnostics and debugging.

About RPG

RPG means Report Program Generator. It is a high-level database access and text generation language invented by IBM for mainframe business environments. It was originally developed by IBM in 1965 as a query tool.

RPG was intended by IBM to facilitate ease of transition for IBM tabulating machine unit record equipment technicians to the new IBM 1401 series of computers.

Tab machine technicians were accustomed to plugging wires into control panels and plug-boards to implement input, output, control and counter operations (add, subtract, multiply, divide). Tab machine programs were executed by impulses emitted in a machine cycle; hence, RPG emulated the notion of the machine cycle with the program cycle.

What is the "program cycle?" This is where RPG's strength lies. Every RPG program executes a loop which applies the program to every record (in the old days, a record was an individual punch card) of a file. Each record is compared to each line in the program. The program would act on the record based on a Yes/No indicator to do a calculation (add, subtract, multiply, divide) or a comparison (equal to, greater than, less than).

Even with the changes from the original RPG through RPG-II, RPG-III, RPG-IV, & RPG/400, RPG retains enough backward compatibility so that an RPG program written in the late 1960s will still run today with little or no modification. Consequently, RPG is one of the few languages created for punch card machines that is still in common use today. Many books on RPG programming are still widely available from commercial publishers. See http://tinyurl.com/5pottb .

RPG programmers insist that the original RPG language is difficult to beat assuming the programmer encompasses all of the available constructs and features.

Although versions of RPG-II and RPG/400 have been produced for MS-DOS and Windows operating systems, there are no free implementations of RPG.… (meer)