TO THE READER

PL/I is a powerful language that can be used to solve both business and scientific
problems. In this text, the PL/I language is presented in as simple and logical
manner as possible . Features that help you grasp the material are incorporated.
For example , checkpoint questions are interspersed throughout each chapter to
determine your comprehension and understanding. (The answers are in Appendix
A . ) A detailed index is provided so that you can quickly reference a technical
point or locate the answer to a question . If you are new to the field of computers, you will find the glossary in Appendix E helpful in looking up the definitions of new
terms. The section on debugging techniques i n each chapter will help you to code
and test you r programs. Each chapter provides a case study and other PL/ I
programs that were compiled using I B M's OS P L/I Optimizing Compiler and
executed under the MVS operating system on an I B M 3 0 8 1 .
TO THE INSTRUCTOR
I t i s almost universally agreed that the best approach for beginning programming
students i s a "structured approach . " In this way, student s learn proper programming
techniques from the beginning, before bad habits are developed . The
techniques that comprise structured programming are stressed throughout the text .
P L/I is s o comprehensive that a 1 0 0 0-page book could b e writ ten and some
things would s t ill be left unsaid. I decided t o present List-Directed f/0 in Chapter
1 so that student s could - after reading only the first chapter of this book actually code a complete (though simple) P L/I program that would compile and
execute. Getting students involved in doing at an early st age of a class gets their
attention, their interest , and their commitment t o the subj ect . The material organized on a " need to know" basis .
Chapter 2, "Top - Down Programming- Internal and External Procedures,"
describes the concept of programming by first defining the criteria of good
programs. The basic structures are described in detail. Then pseudo-code and
stepwise refinement are introduced as alternatives to program flow-charting. The
mechanics of subroutines and functions are introduced in this important chapter
and covered in detail along with recursive programming in Chapter 4.
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Stream I/O is presented before record I/O because that is how i t is taught in many
colleges today. Arrays are presented when the iterative DO is presented; structures
are discussed in the chapter dealing with record I/O, because the need for
structures arises when using the RECORD form of I/O .
On their material in this edition includes a sect ion on list processing, which contains
a case study with a binary tree (Chapter 9), and a section on VSAM file
structure (Chapter 1 0 ) , as well as I SA M and REGIONAL data sets.
The chapters are mostly modular and self-contained, so you can teach according
to your own sequence of topics and assign reading that is not in the sequence
of this book. For example , there would be little if any loss of continuity if you
taught record I/O before stream I/O .
There i s a Teacher's Manual for this text. I t consists of a number of visual aids
suitable for making overhead transparencies for use in the classroom. I t also
contains suggested laboratory problems for each chapter in the book. The manual
is available from the publisher.

Joan K. Hughes