Computer science excels at layering abstraction on abstraction. Our field’s facility for hiding details behind a simplified interface is both a virtue and a necessity. Operating systems, databases, and compilers are very complex programs shaped by forty years of theory and development. For the most part, programmers need little or no understanding of the internal logic or structure of a piece of software to use it productively. Most of the time, ignorance is bliss.
Opaque abstraction, however, can become a brick wall, preventing forward progress, instead of a sound foundation for new artifacts. Consider the subject of this book, programs and programming languages. What happens when a program runs too slowly, and profiling cannot identify any obvious bottleneck or the bottleneck does not have an algorithmic explanation? Some potential problems are the translation of language constructs into machine instructions or how the generated code interacts with a processor’s architecture. Correcting these problems requires an understanding that bridges levels of abstraction.
Abstraction can also stand in the path of learning. Simple questions—how programs written in a small, stilted subset of English can control machines that speak binary or why programming languages, despite their ever growing variety and quantity, all seem fairly similar—cannot be answered except by diving into the details and understanding computers, compilers, and languages.
A computer science education, taken as a whole, can answer these questions. Most undergraduate programs offer courses about computer architecture, operating systems, programming language design, and compilers. These are all fascinating courses that are well worth taking—but difficult to fit into most study plans along with the many other rich offerings of an undergraduate computer science curriculum. Moreover, courses are often taught as self-contained subjects and do not explain a subject’s connections to other disciplines.
This book also answers these questions, by looking beyond the abstractions that divide these subjects. Michael Scott is a talented researcher who has made major contributions in language implementation, run-time systems, and computer architecture. He is exceptionally well qualified to draw on all of these fields to provide a coherent understanding of modern programming languages. This book not only explains language concepts and implementation details with admirable clarity, but also shows how computer architecture and compilers influence language design and implementation. Moreover, it neatly illustrates how different languages are actually used, with realistic examples to clearly show how problem domains shape languages as well.
In interest of full disclosure, I must confess this book worried me when I first read it. At the time, I thought Michael’s approach de-emphasized programming languages and compilers in the curriculum and would leave students with a superficial understanding of the field. But now, having reread the book, I have come to realize that in fact the opposite is true. By presenting them in their proper context, this book shows that programming languages are the true center of computer science, the bridges spanning the chasm between programmer and machine.
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