Whether you are a novice programmer who needs to get up to speed on the ins and outs of CL or an experienced professional looking for a daily CL reference, this comprehensive book is the guide you need.
Here, you'll find all the must-know basics of the CL language, as well as full coverage of its latest and most powerful features — including structured programming capabilities, file processing enhancements, and the Integrated Language Environment (ILE). The book introduces the basics quickly for those without any previous knowledge of CL. Progressing methodically into more complex processes and concepts, it guides readers smoothly toward a professional grasp of CL programming techniques and style.
In addition to 25 chapters covering CL from start to finish, the book includes a condensed reference appendix to the most commonly used CL commands, as well as appendices addressing the essentials of programming tools and debugging. End-of-chapter review questions and programming assignments complete your master course in CL and make the book suitable for use in a classroom or tutorial setting. Students who plan careers as IBM i programming professionals will find this book essential reading.
With Control Language Programming for IBM i, you will:
Learn the role of CL in the IBM i environment
Understand the IBM i user interface and programming tools
Recognize the data types supported by CL, and when to use them
Use program variables, including pointer-based variables and data structures
Use structured statements to organize CL processing and control workflow
Perform program and procedure calls, passing parameters
Understand critical ILE concepts, including procedures and activation groups
Integrate IBM application programming interface (API) programs with CL
About authors
Jim Buck — Jim Buck's career in IT spans more than 25 years, primarily in the manufacturing and healthcare industries. He is a programmer/analyst instructor at Gateway Technical College in Kenosha, Wisconsin; eight-year president of the Wisconsin Midrange Computer Professional Association (WMCPA); co-author of three IBM i textbooks; and the recipient of the 2007 IBM System i Innovation – Education Excellence Award. Jim has been instrumental in creating an advisory board for Gateway's IBM i curriculum, developing classes and seminars in IBM's programming software, and opening networking opportunities for students.
Bryan Meyers — Bryan Meyers is well known to IBM i technicians as the author of a number of popular books and frequent magazine articles. His programming, management, and consulting career has spanned most of the IBM midrange history, from the System/360 through the AS/400 and Power Systems using IBM i. For much of that time, Bryan was the IT director for an international hospitality franchisor. He has also managed computer operations for municipal government, international construction, and broadcasting media industries. Currently, Bryan presents IBM i training to organizations worldwide in a variety of environments, including onsite training, video programs, and online learning. In addition to Programming in RPG IV, his books include Control Language Programming for IBM i (MC Press, 2011) and RPG IV Jump Start (29th Street Press, 2001).
Dan Riehl — Dan Riehl is President of The 400 School, Inc., a leading provider of technical training for IBM i systems. He is also President of the IT Security and Compliance Group, LLC, which provides security consulting, training, and software for IBM i. For more than 20 years, Dan has been a writer and technical editor for System iNEWS magazine, where he writes articles related to system security, system management, and other technical topics.
Contents
CONTENTS
PREFACE
INTRODUCTION TO CONTROL LANGUAGE Chapter 1 What Is CL? Chapter Overview What CL Is What CL Is Not Controlling Workflow with CL CL Execution Environment and Restrictions An Introductory Program Chapter Summary Key Terms Review Questions
Chapter 2 Control Language Command Names Chapter Overview Verbs and Subjects Modifiers and Subject Phrases Command Aliases Chapter Summary Key Terms Review Questions
Chapter 3 Command Parameters Chapter Overview Command Parameters Required and Optional Parameters Entering Parameters with Keyword Notation Entering Parameters with Positional Notation The Order of Parameters Positional Keyword Limits Using *N Mixing Keyword and Positional Notation Types of Command Parameters Parameter Special Values Qualified Values Value Lists Complex Lists Chapter Summary Key Terms Review Questions Exercises
Chapter 4 The IBM i User Interface Chapter Overview The IBM i Menu System Command-Line Operations Command-Line Function Keys The Prompt Facility The Command Prompt Display Determining Allowable Values Command-Prompt Function Keys Additional Parameters Prompt Special Characters Finding the Right CL Command Using the CMD Menus Chapter Summary Key Terms Review Questions Exercises
BASIC CL PROGRAMMING Chapter 5 Creating CL Programs Chapter Overview The Capabilities of CL Programs Using a Source Physical File How to Create a CL Program Adding a Source Member Using WDSc to Add a Source Member Using PDM to Add a Source Member Entering CL Commands into a Source Member Compiling the CL Source Using the CL Compiler CL Compiler Options CL Compiler Reports Analyzing Compiler Reports Diagnosing Compile-Time Errors Diagnosing Errors with WDSc Binding a Program Using a Shortcut CL and the Original Program Model Chapter Summary Key Terms Review Questions Programming Assignments
Chapter 6 The Structure of a CL Program Chapter Overview Entering CL Source Statements Free-Format Statement Entry Upper and Lower Case Blank Lines Keyword and Positional Notation Entering Program Comments Command Continuation (+ and –) Using Labels The Sections of a CL Source Member Program Information Section Program Linkage Section Declarations Section Procedure Section Putting It All Together Chapter Summary Key Terms Review Questions Programming Assignments
Chapter 7 Declaring Program Variables Chapter Overview What Is a Program Variable? How to Declare a Variable The DCL Command Naming Variables Specifying the Data Type Specifying the Variable Size Coding in Style Initializing the Value of a Variable Assigning Values to *CHAR Variables Assigning Values to *LGL Variables Assigning Values to Numeric Variables Miscellaneous Rules for Initial Values Using DCL with Pointers Declaring Based Variables Declaring Defined Variables More DCL Examples The DCLF Command DCLF Examples Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 8 Manipulating Variables with the CHGVAR Command Chapter Overview The CHGVAR (Change Variable) Command Using CHGVAR with Character Variables Using CHGVAR with Numeric Variables Using CHGVAR with Logical Variables Performing Data Conversion with CHGVAR Converting Numeric Data to Character Data Converting Character Data to Numeric Data Using a Variable to Specify VALUE Using an Arithmetic Expression to Specify VALUE Using a Character String Expression to Specify VALUE Using Built-In Functions Using %SUBSTRING Using %BINARY Using Built-In Functions in the Receiver Variable The DMPCLPGM Command Using Functions with Pointers Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 9 CL Control Structures Chapter Overview CL and Structured Programming The GOTO Command IF/ELSE Structure Nested IF Structures Using the ELSE Command Nested IF/THEN/ELSE Structures DO Groups SELECT/WHEN/OTHERWISE Structure Program Looping and Iteration DOWHILE Command DOUNTIL Command DOFOR Command Loops and Early Exits Using Subroutines The CALLSUBR Command Leaving a Subroutine Using a Return Value The DCLPRCOPT Command Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 10 Expressions Chapter Overview What Is an Expression? Using Arithmetic Expressions Arithmetic Order of Operations Using the %BIN Function Using Character String Expressions Using the %SST Function Using Relational Expressions Relational Operators Character Operands of Different Lengths Using Relational Expressions with the CHGVAR Command Using Logical Expressions Evaluating Logical Relationships Using Logical Variables and Logical Constants Using More Than Two Operands Expression Order of Evaluation Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 11 Controlling Workflow Chapter Overview Work Management Overview What Is a Job? What Is a Job Description? What Is a Job Queue? What Is a Library List? Executing Programs with the CALL Command ILE Considerations The Call Stack Executing Programs with the TFRCTL Command The RETURN Command High-Level Language Considerations Executing Commands in Batch Using SBMJOB The CMD Parameter of the SBMJOB Command Other SBMJOB Parameters Job Definition Parameters for SBMJOB Library List Parameters for SBMJOB SBMJOB Output Parameters Scheduling Parameters for SBMJOB The Self-Submitting Program Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 12 Basic Error Handling Chapter Overview Types of Errors Error Messages Message Files The CHKOBJ Command The MONMSG Command Command-Level MONMSG Program-Level MONMSG Mixing Command- and Program-Level MONMSGs Monitoring for Generic Messages Specifying Multiple MONMSG Commands Errors Within a MONMSG The Interactive Job Log Ignoring Error Messages Receiving Escape Message Text Chapter Summary Key Terms Review Questions Exercises Programming Assignments
INPUT/OUTPUT IN A CL PROGRAM Chapter 13 Passing Parameters Chapter Overview What Are Parameters? Defining Parameters in a Called Program Passing Constants to a Called Program Passing Character Constants Passing Logical Constants Passing Decimal Constants Passing Variables to a Called Program The Mechanics of Passing Variables Passing Parameters Using the TFRCTL Command Passing Parameters Using the SBMJOB Command Using Hexadecimal Notation Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 14 Retrieving and Changing External Attributes Chapter Overview Return Variables The RTVJOBA Command The CHGJOB Command System Values The RTVSYSVAL Command The CHGSYSVAL Command Categories of System Values Date/Time System Values System Control System Values Library List System Value Other System Values The RTVUSRPRF Command The CHGUSRPRF Command Other RTV Commands Date Conversion Using the CVTDAT Command Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 15 Files and Data Areas Chapter Overview Working with Files Database Files Display Files CL and SQL File Existence Requirements for CL Data Description Specifications DDS for Physical Files DDS for Logical Files DDS for Display Files Files Without DDS CL File Processing The DCLF Command The SNDRCVF Command The SNDF Command The RCVF Command The WAIT and ENDRCV Commands CL OUTFILE Support Data Areas Creating and Deleting a Data Area Displaying a Data Area's Contents Retrieving the Contents of a Data Area Changing the Contents of a Data Area The Local Data Area Chapter Summary Data Queues Key Terms Review Questions Exercises Programming Assignments
ADVANCED CL PROGRAMMING Chapter 16 Advanced Message Handling Chapter Overview Messages What Is a Message? Message Queues Types of Messages Commands Used to Send Messages The SNDMSG Command The SNDBRKMSG Command The SNDPGMMSG Command The SNDUSRMSG Command Receiving Messages The TOPGMQ Parameter RCVMSG Examples Removing Messages RMVMSG Examples Standard Error-Handling Routines Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 17 Advanced File Techniques Chapter Overview Using Files in a CL Program Using File Overrides Using the OVRDBF Command Using the DLTOVR Command Using the OVRPRTF Command Positioning Database Files Preopening Database Files Using OPNQRYF Using CPYFRMQRYF Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 19 Using IBM-Supplied APIs Chapter Overview Introduction to APIs Using QCMD Using QUSCMDLN Using QCMDCHK Prompting with QCMDCHK Using QCMDEXC QCMDEXC and Call Levels Other APIs ILE Bindable APIs Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 20 Displaying and Changing Command Properties Chapter Overview Displaying the Properties of a CL Command Changing the Properties of a CL Command Changing Parameter Default Values Changing IBM-Supplied Commands Chapter Summary Key Terms Review Questions Exercises
Chapter 21 Understanding the Job Log Chapter Overview What Is a Job Log? The LOG Attribute Logging CL Commands Analyzing the Job Log Keeping a Lean Job Log Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 22 Understanding the Integrated Language Environment Chapter Overview What Is ILE? What Is a Procedure? What Is a Module? What Is a Program? Creating ILE Modules and Programs One-Step Program Creation Multiple-Module Programs Updating ILE Programs Adding Modules Calling ILE Programs and Procedures Calling ILE Procedures Using a Static Call Using Service Programs Understanding Activation Groups Default Activation Group User-Named Activation Group System-Named Activation Group *CALLER Activation Group Option *ENTMOD Activation Group Option Activation Groups Made Easy Activation Groups and File Overrides Call Stack Level Scoping Activation Group Scoping Job Scoping ILE Error Handling ILE Error-Handling Tips Chapter Summary Key Terms Review Questions Exercises Programming Assignments
CREATING YOUR OWN COMMANDS Chapter 23 User-Defined Commands Chapter Overview Why Commands? The Components of a Command Command Definition Statements The CMD Statement The PARM Statement The QUAL Statement Other Command Definition Statements The CRTCMD Command Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 24 Command Processing Programs Chapter Overview Writing a Command Processing Program Parameters in the CPP Analyzing the CPP Processing List Parameters in the CPP Using QCMDEXC as a CPP Chapter Summary Key Terms Review Questions Exercises Programming Assignments
Chapter 25 Advanced Command Facilities Chapter Overview Adding Help to Your Commands Using the GENCMDDOC Command UIM Tag Language Associating a Panel Group with a Command Validity Checking Programs Other Advanced Command Topics Chapter Summary Key Terms Review Questions Exercises Programming Assignments
APPENDICES Appendix A The Most-Often-Used CL Commands Appendix B Program Development Tools Appendix C Program Testing and Debugging
Jim Buck —
Bryan Meyers —
Dan Riehl —
