This textbook has been developed for first semester students of Hardware and Software of personal Computers. It will also be of interest to practicing engineers and professionals who wish to develop their own hardware and software for special PC-based application. Apart from providing all the significant hardware and software details for IBM-PCs and its close compatibles, it also presents a comprehensive description of how the PC works and the various functions that it can provide. A large number of interesting and useful problems have been given at the end of each chapter. A set of objective type questions has also been provided to allow the readers to review their understanding of the material in the textbook.