Code by Charles Petzold

I've been using computers for decades, but Code by Charles Petzold helped me understand them on a deeper level. It starts with the very basics of communication using code. Morse code, Braille, telegraphs, boolean logic. From there it gradually builds up, layer by layer, to the technologies used in modern computers. By the end you've gone from flashlights and electrical circuits to memory, processors, and operating systems. The progression feels natural, which is impressive given how much ground it covers. The history woven throughout is part of what makes it work. If you've ever been curious about why ASCII works the way it does, how it evolved into Unicode, or why bytes are eight bits, Petzold doesn't just explain the technical answer. He explains the human decisions that got us there. A couple of chapters were a bit of a slog (the deeper circuit-building sections especially), but overall it kept me interested enough to finish. As someone without a Computer Science degree, it was satisfying to have the layers of abstraction pulled back to the 1s and 0s. Not because I need to think at that level day to day, but because understanding the foundation makes everything above it a little less mysterious. If you write software but have ever felt a gap between what you do and how the machine actually does it, this book fills in a lot of that space.