Like its DOS predecessors, OS/2 provides a batch language capability for storing and invoking programs composed of operating system commands. OS/2 also permits such programs to be written in REXX, a general-purpose structured programming language designed specifically for writing operating system command procedures. REXX was developed originally for the host-based VM/CMS operating system, and has been implemented on many platforms. Its appearance in OS/2 indicates that it has successfully made the transition to the PC world.

This book is intended for OS/2 users who are pushing the limits of the system’s batch language facilities. It supplements the OS/2-supplied material on REXX by providing a task-oriented exposition of the REXX language and a wealth of REXX examples. Roughly one-third of the book is devoted to sample programs, and another 200 or so programs are included in the diskette supplied with the book. The diskette provides a painless way of using existing programs as the seeds for building new ones.

Separate chapters are devoted to the tasks encountered in writing command programs: communicating with the user, issuing commands to the operating system, working with strings, using external data queues, and so forth. Other chapters describe particular REXX constructs, such as keyword instructions and built-in functions. This mixture of task-oriented and language-oriented material helps in learning to use the language, but it tends to obscure the structure of the language, and it makes the book difficult to use as a language reference. For example, because of the large number of REXX built-in functions, the author has grouped them into task-oriented categories, such as bit manipulation, exception handling, and file management. A list of functions in each category is provided, but no single list of all the functions is given. To determine if REXX provides a built-in function for performing a particular task, the reader must either guess which category the author has placed the function in or scan multiple lists.

The book deals exclusively with REXX in the OS/2 environment, and considerable space is devoted to OS/2 facilities that support the use of REXX. These include the OS/2 Enhanced Editor and Icon Editor (a large number of icon files are provided on the diskette); OS/2 batch commands and their REXX equivalents; external functions for screen and file management; an interactive REXX instruction executor; and a windowed Presentation Manager application for invoking REXX programs.

The chief value of this book lies in its specific orientation to OS/2 users, and in the extensive examples that it provides. As a source of information about REXX per se, the reader would do better to stick with the old standbys, such as Cowlishaw [1]. Readers already familiar with REXX should beware of terminology switches; for instance, keyword instructions are almost always referred to as “statements.” The purpose of these changes is not explained, but it may have to do with compatibility with OS/2 batch command terminology, or with some perceived deficiency in the original REXX terminology.