http://www.amazon.com/exe…=books&n=507846
I just finished an excellent book, Code: The Hidden Language of Computer Hardware and Software by Charles Petzold. It’s well written, and I highly recommend it to anyone curious about digital logic, assembly language, and other topics about how computers really work. I’ve never had formal schooling in these subjects, and I don’t believe it is necessary in order to enjoy this book. I wrote an email to the author this morning.
Dear Mr. Petzold,
One fine, clear evening my wife and I were strolling around downtown Seattle. At Barnes and Noble I was lucky enough to pick up a copy of your book, “Code”.
Thank you. Thank you for writing this book! I just completed it, and am happy to say that I feel strengthened in my understanding of how computers really work. I enjoyed the examples, the humor and the simple, straightforward explanations. It is amazing to see what can be built by combining simple, tangible objects with novel ideas.
I do have a question about something you mention on page 353. Quoted: “An example: Many processors have bit-shifting instructions. As you’ll recall, these instructions shift the bits of the accumulator to the right or left. But almost no high-level programming languages include such operations.”
I believe a clarification is necessary. I’m familiar with Java, Perl, Bash Scripting, and Python. All of these high-level programming languages are quite popular, and all have bit-shifting operations.
Sincerely,
-Adam Monsen
And in a couple of hours he wrote back! What a cool guy.
Thank you very much. When “Code” was first published I figured that this was at least one book I’d never have to revise. Maybe that’s not entirely true….
When I wrote that passage, I was undoubtedly thinking in the long view. I was considering primarily the classic procedural languages such as Cobol and Fortran and Algol and Basic and Pascal and PL/I, and the many, many other languages discussed in the 785-page “Programming Languages: History and Fundamentals” by Jean B. Sammet and published a long, long time ago in 1969.
Of course, I knew at the time of one *major* exception to the “no bit-shifting” rule, and that is C (as I discuss ten pages later). It was primarily because of C that I said “almost no.” Of course, C has been a highly-influential language, as is evident with your list of bit-shifting languages. You might also have included C++ and C#.
I’m not sure how I’d change that passage today. Perhaps instead of “But almost no…” I’d say “Historically, few high-level programming languages have included such operations, although C and many recent languages influenced by C implement bit-shifting instructions.”
Charles
This book is not for the easily distracted. I had to read over some of the examples many times before I felt like I really “got” them. The effort was well worth it, and I’m glad I discovered this book! If you’re ready to dig in and really understand how the computer works, check it out.
This book might be thought of as a “beginner’s tutorial to assembly language”. Many pages are spent explaining the purpose and function of machine language and data.