This book introduces the concepts of diverse programming languages for students who have already mastered basic programming in at least one language. It is suitable for use in an undergraduate course for computer science and computer engineering majors. It treats all the knowledge units in the area of programming languages that appear in the ACM's Computer Science Curriculum 2008, and introduces the core units thoroughly. It gives programming exercises in three different language paradigms. Philosophically, it is in complete agreement with the ACM report. This book has two distinct kinds of chapters: practical and theoretical. The practical chapters are self-contained primers in three very different programming languages - ML, Java, and Prolog - at least two of which will be new languages for almost all students at this level. Students receive a quick introduction to the linguistically unique parts of each language and enough simple programming exercises to develop a feel for the programming paradigm of the language. There are excellent free implementations of all these languages available on a variety of platforms, including Windows, Unix, and Macintosh; the book's Web site at http://www.webber-labs.com/mpl.html has instructions on how to get them. The theoretical chapters present the underlying principles of programming languages. They are interleaved with the practical chapters in an order that allows ideas to be illustrated using examples in the newly learned languages and allows theoretical topics to be covered when their relevance to programming practice will be most evident. For example, Chapter 23 deals with formal semantics by starting with simple interpreters written in Prolog. These interpreters lead naturally to language definitions using big-step operational semantics. That is why formal semantics occurs so late in the book: only at the end of the Prolog tutorial are students ready to be led from Prolog exercises to this related, abstract topic.

This book has two major goals. The first is to help you understand and appreciate the beautiful and enduring ideas of formal language. These ideas are the birthright of all computer scientists, and they will profoundly change the way you think about computation. They are not only among the most beautiful, but also among the most useful tools in computer science. They are used to solve problems in a wide variety of practical applications, and they are especially useful for defining programming languages and for building language systems. The second purpose of this book is to help you develop a facility with these useful tools. Our code examples are in Java, but they are not particularly Java-centric and should be accessible to any programmer. There is also a third major reason to study formal language, one that is not a primary focus of this book: to learn the techniques of mathematical proof. When you are learning about formal language, it can also be a good time to learn proof techniques, because the subject is full of theorems to practice on. But this book tries to make the beautiful and useful ideas for formal language accessible to students at all levels of mathematical interest and ability. To that end, although the book presents and discusses many simple proofs, it does not try to teach advanced proof techniques. Relatively few of the exercises pose challenging proof problems. Those planning graduate-level study of theoretical computer science would be well advised not to rely exclusively on this book for that kind of training.