Introduction

This book is concerned with abstract models of computation. Several new models of computation have emerged in the last few years (e.g., chemical machines, bio-computing, quantum computing, etc.). Also, many developments in traditional computational models have been proposed with the aim of taking into account the new demands of computer system users and the new capabilities of computation engines. A new model of computation, or a new feature in a traditional one, usually is reflected in a new family of programming languages and new paradigms of software development. Thus, an understanding of the traditional and emergent models of computation facilitates the use of modern programming languages and software development tools, informs the choice of the correct language for a given application, and is essential for the design of new programming languages.