The fourth edition of this widely used book includes several new topics to make the coverage more comprehensive and contemporary. The book presents an exhaustive and up-to-date exposition of CPUs, peripherals, supporting chips and bus standards. The coverage of Architecture and Microprocessors thoroughly revised and expanded to include contemporary chips and devices. The discussion of memory expanded to include recent developments like cache memory, SD RAM, SG RAM, Smart hard disks, Super floppy, ZIP-Plus drives, DVD-ROM and MO disks. Contemporary input devices and printers highlighted. Software section expanded to include Visual BASIC, C++, Java, OOP, SQL, Windows, Linux and MS-Office. Biased exponent included and present day computer applications highlighted. With its simple style and broad coverage, this book is an essential text for undergraduate science and engineering students. AMIE candidates as well as BCA, MCA and PG-DCA students would also find it very useful.