Peter Landin remarked long ago that the goal of his research was “to tell beautiful stories about computation”. Since then many researchers have told many such stories. This book is a collection my favorites in the area of languages for programming and program specification.

In 1992, the Computer Science Department of Carnegie Mellon University replaced the preliminary examinations for its doctoral students by a set of required courses, including CS711, simply titled “Programming Languages”, which was intended to be a unified treatment of the basic principles of the subject. Previously, such material had been divided between the programming systems examination and the theory examination, and many important topics had fallen through the cracks between the syllabi. (For example, students were expected to know enough of the theory of program proving to understand Cook completeness, yet they never saw the proof of an actual program beyond a trivial one that computed a square root by iterating over successive natural numbers and squaring them.)

As the most vociferous exponent of such a course, I was put in charge of teaching it, and I soon discovered that there was no suitable textbook. Serious texts in areas such as semantics or verification invariably stressed a particular approach and neglected topics that did not fit well with their point of view. At the opposite extreme, surveys of programming languages usually emphasized superficial differences between languages while slighting more fundamental issues. In effect, what was available were profound novels and journalistic popularizations, but what was needed was a collection of short stories sharing some common characters. Thus I produced extensive class notes, which in a few years grew into this book.