For sophomore/junior-level courses on Microprocessors, Embedded Control Systems, and Microprocessor Interfacing. Emphasizing architecture and programming (rather than electrical details), this text examines the hardware and software features of the MCS-51 family of microcontrollers. Comprehensive, clear, and concise, it starts at a rudimentary level - What is a microprocessor? What is a microcontroller? - and evolves to encompass complete, finished design examples using such software tools as the assembler (ASM51), the linker (RL51), and the object-to-hex conversion utility (OH). Along the way, students complete a hands-on, easy-to-build project - a simple single-board, 10-chip computer - that develops into a working prototype 8051 computer that can be used in the classroom or lab to demonstrate principles.