This textbook provides a concise yet comprehensive introduction to how computers are organized and how their architectural design works. It covers fundamentals like data representation, logic circuits, instruction set architectures (with examples such as the MARIE simulated computer), memory systems, I/O and storage, system software, and embedded architectures. Real-world applications and up-to-date technologies (e.g. tablets, cloud computing) are included; the book is suitable for a one-term course.