Preface

In today’s world, much emphasis is placed on learning to code, and programming is touted as a golden ticket to a successful life. Despite all the code boot camps and programming being taught in elementary schools, the computer itself is often treated as an afterthought — it’s increasingly becoming invisible in the discussions of raising the next generations of computer scientists.

The purpose of this book is to give readers a gentle yet accessible introduction to computer systems. To write effective programs, programmers must understand a computer’s underlying subsystems and architecture. However, the expense of modern textbooks often limits their availability to the set of students that can afford them. This free online textbook seeks to make computer systems concepts accessible to everyone. It is targeted toward students with an introductory knowledge of computer science who have some familiarity with Python. If you’re looking for a free book to introduce you to basic computing principles in Python, we encourage you to read How To Think Like a Computer Scientist with Python first.

If you’re ready to proceed, please come in — the water is warm!

Our book is titled Dive into Systems and is meant to be a gentle introduction to topics in computer systems, including C programming, architecture fundamentals, assembly language, and multithreading. The ocean metaphor is very fitting for computer systems. As modern life is thought to have risen from the depths of the primordial ocean, so has modern programming risen from the design and construction of early computer architecture. The first programmers studied the hardware diagrams of the first computers to create the first programs.

Yet as life (and computing) began to wander away from the oceans from which they emerged, the ocean began to be perceived as a foreboding and dangerous place, inhabited by monsters. Ancient navigators used to place pictures of sea monsters and other mythical creatures in the uncharted waters. Here be dragons, the text would warn. Likewise, as computing has wandered ever further away from its machine-level origins, computer systems topics have often emerged as personal dragons for many computing students.

In writing this book, we hope to encourage students to take a gentle dive into computer systems topics. Even though the sea may look like a dark and dangerous place from above, there is a beautiful and remarkable world to be discovered for those who choose to peer just below the surface. So too can a student gain a greater appreciation for computing by looking below the code and examining the architectural reef below.

We are not trying to throw you into the open ocean here. Our book assumes only a CS1 knowledge and is designed to be a first exposure to many computer systems topics. We cover topics such as C programming, logic gates, binary, assembly, the memory hierarchy, threading, and parallelism. Our chapters are written to be as independent as possible, with the goal of being widely applicable to a broad range of courses.

Lastly, a major goal for us writing this book is for it to be freely available. We want our book to be a living document, peer reviewed by the computing community, and evolving as our field continues to evolve. If you have feedback for us, please drop us a line. We would love to hear from you!

Our textbook covers a broad range of topics related to computer systems, specifically targeting intermediate-level courses such as introduction to computer systems or computer organization. It can also be used to provide background reading for upper-level courses such as operating systems, compilers, parallel and distributed computing, and computer architecture.

This textbook is not designed to provide complete coverage of all systems topics. It does not include advanced or full coverage of operating systems, computer architecture, or parallel and distributed computing topics, nor is it designed to be used in place of textbooks devoted to advanced coverage of these topics in upper-level courses. Instead, it focuses on introducing computer systems, common themes in systems in the context of understanding how a computer runs a program, and how to design programs to run efficiently on systems. The topic coverage provides a common knowledge base and skill set for more advanced study in systems topics.

Our book’s topics can be viewed as a vertical slice through a computer. At the lowest layer we discuss binary representation of programs and circuits designed to store and execute programs, building up a simple CPU from basic gates that can execute program instructions. At the next layer we introduce the operating system, focusing on its support for running programs and for managing computer hardware, particularly on the mechanisms of implementing multiprogramming and virtual memory support. At the highest layer, we present the C programming language and how it maps to low-level code, how to design efficient code, compiler optimizations, and parallel computing. A reader of the entire book will gain a basic understanding of how a program written in C (and Pthreads) executes on a computer and, based on this understanding, will know some ways in which they can change the structure of their program to improve its performance.

Although as a whole the book provides a vertical slice through the computer, the book chapters are written as independently as possible so that an instructor can mix and match chapters for their particular needs. The chapter dependency graph is shown below, though individual sections within chapters may not have as deep a dependency hierarchy as the entire chapter.

Dive into Systems can be used as a primary textbook for courses that introduce computer systems topics, or individual chapters can be used to provide background information in courses that cover topics in more depth.

As examples from the authors' two institutions, we have been using it as the primary textbook for two different intermediate-level courses:

Additionally, we use individual chapters as background reading in many of our upper-level courses, including:

Finally, Chapters 2 and 3 are used as C programming and debugging references in many of our courses.

The free online version of our textbook is available at https://diveintosystems.org/.