Code

As many other reviews said, the first part of the book is a brilliant, entertaining, easily understandable & accessible overview of underlying topics that relate to how "codes", electronic signals, alternate number systems & computers came about. The latter sections are considerably more dense, and required going back a few times, tracing the circuit diagrams with my finger, and Googling the finer points of electrical circuitry, how to do math in binary, octal, and hexadecimal, and other assorted topics covered in this wide-ranging work. I had classes a LONG time ago in electrical engineering, as well as a good amount of experience with binary, hex(adecimal), and programming, so given that background I could follow along fairly easily & connect the concepts to my existing knowledge. If you don't have any background at all in EE, Comp Sci, or programming, be prepared to re-read & re-re-read the chapters on logic gates, circuits, and how these bits of hardware physically compute & store basic arithmetic values in order to perform complex tasks. Those sections were the most challenging, but ultimately for me provided the most valuable information because it helped fill in the missing pieces of the puzzle in my prior knowledge. For anyone who wants to "learn to code," but you find yourself confused by or not really bothering to understand concepts like pointers, memory addresses, Boolean logic, or esoteric & ancient magic spells like "XOR" or Assembly Language, this book does an excellent job of explaining in real, physical hardware terms exactly what those mean and how they work. My only critique is that after ALL that fine-grained detail & historical backstory for most of the book, the final chapter crams roughly the last 40 years of computing into a few short pages, covering everything from Graphical User Interfaces & image compression to the internet & (rather outdated) descriptions of web browsers. It felt rushed & tacked on. I'd really like to see an update, or a companion book, that covers newer topics in such detail as the first half of this book. Overall though, this was a fantastic, educational if at-times-dense read. I had to work at it a bit, but that was the point. If you hate to read, don't want to learn, and are too lazy to work at it - buy it anyway to give him another $15 and then write a review explaining why it's the book/author's fault :P

I am a computer programmer by trade and sincerely wish I had this book 7 years back when I started formal education. During my 4+ years in the higher education system, and even after, I and my classmates (later colleagues) were taught how to program computers (in various languages) and many of the higher level ideas in programming (Data Structures, Algorithms, Program Structure, Etcetera, Etcetera, Etcetera) but we never really learned how the computers worked inside. Even to many trained programmers, or at least me:), these beige boxes can be something of a magical black box which we don't really understand at a fundamental beyond the point of it processing the instructions we give it in our chosen programming language. In school I recieved perhaps one single semester course that attempted to teach how these things worked inside, yet that course still skimmed on the inner workings, the teacher instead spent his time on how monitors drew pixels on the screen and how laser printers worked..... Looking back on it, I would blame the ignorance of the inner workings of computers that some programmers have on the decline of having to learn Assembly language (starting in the early nineties?), the lowest level programming language sans actual Machine Code, where one would be forced to deal with the raw inner workings of a computer naturally. I myself hope to learn it one day after reading this book :D Instead, I was taught the C programming language and what we learned in school became only more abstract in regards to the actual hardware... This is where this wonderful book came into play. Since I recieved it half-a-year ago, it must have been read/devoured by me a dozen times or more - it goes from teaching the make-up of various codes (morse, braille, etcetera) to showing how some simple to understand concepts can be combined until a working computer, calculator, etcetera, can be built....... it gives one a great foundation for learning what Computer Science is all about or gives a newer-generation Programmer, like me, much needed knowledge on how that beige box basically works, on a hardware level! The best thing is that those computer analogies can be finally thrown out the window - we all heard them before - like how "ram is like a table, or workspace. The bigger it is, the more things you can have ready and available at one time. The hard drive is like your drawers and cabinets. You can store more stuff there, but to use it, you have to take it out first and put it either on the table (RAM) or hold it in your hand (cache)." Petzold also uses analogies when he introdues topics but quickly moves beyond them, giving his audiences real understanding of the subject - which is very welcoming since analogies tend to explain function well but break down quickly when one is determined to learn more about a topic. It is probably one of the few computer books on my shelf that can't get outdated and that's good, because it still will be there in 20 years.

小学生のころから、パソコンは電気で動く、電気で計算している、２進数も電気のオン・オフで表現される、といった話は聞いていましたが、具体的な仕組みは知りませんでした。 例えば、NOTゲートは、入力が「０」（電気が流れてこない）なら出力は「１」になる（電気が流れ出ていく）わけですが、この出ていく電気はどこから湧いたのでしょうか？ 逆に、入力が「１」なら出力は「０」ですが、入ってきた電気はどこに消えたのでしょうか？ こういったことは、真理値表や論理回路の記号を眺めていただけでは分かりません。 この本、Charles Petzoldの『Code』は、小学校で習うような電気回路から、論理ゲート、メモリ、CPUなど（の実物よりかなり大きなモデル）を組み立てる方法を説明し、ブラックボックスだったコンピュータの中身を目で見えるようにしてくれます。 NOTゲートの例についても、そこに繋がっている導線が、実は、入力用と出力用の２本以外にもあり、魔法が使われているわけではないということが分かるようになります。 その他の疑問も、私の場合は、この本でほとんど解消しました。特に、コンピュータによる「計算」とは懸け離れているように感じられる周辺機器（ディスプレイやプリンタ）の制御方法にも簡単に触れられていて、「考えた人すごい！」と思いました。もちろん、これを分かりやすく説明してくれる著者もすごいのですが。 というわけで、コンピュータの大体の構成は理解したうえで、それが実際にはどう実現されているのか具体的に知りたい、という方にはぜひ読んでみていただきたい本です！ 洋書ですが、平易な英語で書かれているので、コンピュータ用語になじみがあれば、すらすら読めるはずです。「試し読み」で確認してみてください。（「Preface」だけは少し難しめかもしれませんので、本文で判断されることをお勧めします。）

Simply the best introduction to fundamental computing from an electronics perspective to those without a formal Comp. Sci. degree there is in my opinion. As a Perl programmer - and one could say any high level programming language - I am abstracted from the hardware so have no real idea of what goes on 'in the engine' compartment. True, a lot of the information is now historic and is utterly unnecessary to know in these days of virtualised cloud computing on demand with pay-per use billing....but for those interested it is an insight to that now passing (passed?) era of 'the Before Time'. This book has a very smooth, swallow learning curve - more a 'learning line' - and goes from a simple on-off telegraph relay used as a transmission device all the way through how n-bit adders and '1s complement' is used to to interact with memory blocks to do subtraction through to their implications and use in assembly language with registers of modern processors. The section on coding of language (Braille is used as an example) is also enlightening. From the discussions I've had with others who have done formal Computer Science degrees (I haven't - yet) this book covers a sizable chunk of the fundamental computing topics. After reading this book I will never look at a division operation in one of my programs in the same way again!

É um livro que te introduz à muitos conceitos de computação de forma muito clara e lúdica. Ele não é um livro pesado que você precisa ler enquanto faz várias anotações e pesquisa vários termos. Ele é realmente um livro introdutório, se você está começando ou já trabalha com computação e quer aprender esses conhecimentos básicos, esse é provavelmente um dos melhores livros. Mesmo na UFRJ as aulas não são tão claras e tão aprofundadas como esse livro, que em seu 12º cápitulo já explica ADDER usando circuitos lógicos, algo que eu não vi cursando ciência da computação na UFRJ, com matérias que utilizavam circuitos lógicos.

Only a few chapters in, but I'm enjoying it so far. The first few chapters I've been skimming quite a bit because the concepts are very simple and some of the paragraphs are somewhat repetitive. It does give you a good understanding of how the simple concepts build up to form complex systems. But that's only what I've read so far.

Things taught in university is covered in here and described in a way that's easily comprehensible.