This book covers the hardware, software and applications of microcomputers. A microprocessor based system requires understanding of both hardware and software. Here more emphasis has been given on software so that one can cope with the rapid expansion in the field of microprocessors. The book also explains each mnemonic to make the reader understand the physical phenomena taking place in the hardware circuitry of the microprocessors. Interfacing techniques have been explained clearly with the aid of diagrams, charts and tables alongside the input output devices and controlling and peripheral devices.