This textbook introduces the reader to assembly language programming and its role in computer programming and design. The focus is on providing students with a firm grasp of the main features of assembly programming, and how it can be used to improve a computer's performance. The revised edition covers a broad scope of subjects and adds valuable material on protected-mode Pentium programming, MIPS assembly language programming, and use of the NASM and SPIM assemblers for a Linux orientation.  All of the language's main features are covered in depth. A particular strength is the discussion of the improvements in performance that can be achieved using assembly programming where appropriate. The exposition is motivated by numerous pedagogical tools, including examples, hands-on exercises, programming code analyses and challenges, chapter summaries, and helpful appendices.