Code: The Hidden Language of Computer Hardware and Software

Petzold's approach is brilliant in its simplicity. By starting with things everyone understands, such as signalling with flashlights or building simple circuits with batteries and bulbs, he makes each step feel obvious, and by the end readers have climbed all the way to a working processor without ever feeling lost. Each chapter builds directly on the last, so readers who take their time will find that nothing is skipped or taken for granted.

The middle chapters on binary numbers, logic gates and adding machines are the heart of the book, and the moment when simple switches combine to perform arithmetic is genuinely exciting. Petzold also weaves in history, from Samuel Morse to the early computer pioneers, which gives the technical explanations a human context.

The later chapters, on software and operating systems, move faster and feel more dated in the first edition, and some readers find the electronics detail in the middle demanding. A revised second edition appeared in two thousand and twenty-two with updated material. For anyone who wants to truly understand computers from the ground up, it is a classic. About 400 pages in the Microsoft Press paperback.