The IBM i Control Language, commonly referred to as CL, is the human interface to one of the most successful computing platforms ever. For this reason, mastery of this language is necessary to get the greatest benefit from the IBM i server. This book helps IT professionals--programmers and system administrators--who use IBM i to get the most out of the platform, by showing them how to write useful CL programs. This new edition of the book has been updated for IBM i 7.3 and includes new built-in functions, new data types, and new support for SQL. Upon completion of this book, the reader will be able to: * Write robust, production-grade programs in the IBM i Control Language * Compile CL programs and modules, and combine modules into programs * Handle unexpected errors in a graceful manner * Use powerful built-in functions with character and numeric data * Use looping and decision structures * Access the database effectively * Use messaging for program-to-program and program-to-user communication.